Methods, systems, and computer program products for determining a property of construction material

ABSTRACT

Methods, systems, and computer program products for determining a property of construction material. According to one aspect, a material property gauge operable to determine a property of construction material is disclosed. The gauge may include an electromagnetic sensor operable to measure a response of construction material to an electromagnetic field. Further, the electromagnetic sensor may be operable to produce a signal representing the measured response by the construction material to the electromagnetic field. An acoustic detector may be operable to detect a response of the construction material to the acoustical energy. Further, the acoustic detector may be operable to produce a signal representing the detected response by the construction material to the acoustical energy. A material property calculation function may be configured to calculate a property value associated with the construction material based upon the signals produced by the electromagnetic sensor and the acoustic detector.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/712,754, filed Aug. 30, 2005, and U.S.Provisional Patent Application Ser. No. 60/719,071, filed Sep. 21, 2005,the disclosures of which are incorporated by reference herein in theirentireties. The disclosure of U.S. patent application No. ______entitled METHODS, SYSTEMS, AND COMPUTER PROGRAM PRODUCTS FOR MEASURINGTHE DENSITY OF MATERIAL, simultaneously filed herewith, is incorporatedby reference in its entirety.

TECHNICAL FIELD

The subject matter described herein relates to measuring materialproperties. More particularly, the subject matter described hereinrelates to methods, systems, and computer program products fordetermining a property of construction material.

BACKGROUND

An important aspect of construction engineering is road construction andmaintenance. The ability to design and construct roads based on futureloads and environmental factors is very important as it saves time,effort, and resources in future maintenance costs. A well-designed roadwill have long-term performance when the design factors of loading,climatic, and soil conditions are accounted for properly.

In construction engineering, some of the most important properties ofinterest are volumetric and mechanistic properties of constructionmaterials such as soil, asphalt, concrete, and the like. In particular,there are procedures in construction engineering practice that relatetotal volume V_(t), mass of water M_(W), and mass of dry solids M_(S) tothe performance of a structure built on a soils foundation. Otherimportant properties of interest are mechanical properties such asstiffness, modulus, and density. Thus, the measurements of theseproperties are important for construction engineering.

Asphalt and cement mixes used for construction typically remainrelatively homogeneous and are well behaved unless problems such assegregation arise. In general, well-controlled materials can provide forthe ability to calibrate non-nuclear and nuclear surface gauges withrelatively good confidence. On the other hand, in most geographic areas,soils are inhomogeneous, and the earthwork required to excavate and fillon construction projects typically leads to areas and layers of soil ofdifferent mineralogy, moisture content, gradation, and texture. Theresult is that indirect methods of measurement, such as surfaceelectromagnetic or acoustic instruments, frequently need recalibrationwhen the operator suspects something in the base construction materialhas changed.

One of the most robust construction material measurement tools currentlyavailable is a nuclear density gauge. However, even this equipment issusceptible to limited errors as a result of the chemical compositioneffects. The largest error for nuclear techniques is in the watercontent which is used to correct the wet density measurement. If thecomposition under the gauge becomes richer in hydrogen than the originalcalibration site, then recalibration is necessary. For instance micaloaded clay and sand-like materials have different chemicalcompositions, and would need different moisture offsets or corrections.The problem comes when the clay/sand or mineral content variesthroughout the scope of the project.

It is the purpose of the semi-empirical and mechanistic design methodsto link laboratory tests and design criteria with the material work inthe field. For instance, if a soil fails a laboratory resilient modulus(RM) test, the soil could be replaced with fill or strengthened withlime or cement. In the field, the soils are not typically homogenous,and can change as a result of climatic conditions such as temperatureand moisture. For this reason, it is desirable to have quality controlinstrumentation and methods that can adjust for temperature and/ormoisture effects. The results of such data can be helpful toconstruction personnel for determining soil and asphalt areas of lowquality.

Techniques are known for measuring the modulus of constructionmaterials. Generally, the measurements are obtained by generating anacoustic disturbance in the construction material and measuring aresponse of the material to the disturbance. For example, wavevelocities of the response to the acoustic disturbance may be measuredfor determining modulus. However, the determined modulus in thesetechniques are subject to inaccuracies. It is desirable for providingcorrection to modulus measurements and generally improving the accuracyof modulus measurements of construction material.

Accordingly, in light of the above described difficulties and needsassociated with nuclear density gauges, there exists a need for improvedmethods, systems, and computer program products for a property ofconstruction material.

SUMMARY

According to one aspect, the subject matter described herein includesmethods, systems, and computer program products for determining aproperty of construction material. According to one aspect, a materialproperty gauge may be operable to determine a property of constructionmaterial. The gauge may include an electromagnetic sensor operable tomeasure a response of construction material to an electromagnetic field.Further, the electromagnetic sensor may be operable to produce a signalrepresenting the measured response by the construction material to theelectromagnetic field. An acoustic detector may be operable to detect aresponse of the construction material to the acoustical energy. Further,the acoustic detector may be operable to produce a signal representingthe detected response by the construction material to the acousticalenergy. A material property calculation function may be configured tocalculate a property value associated with the construction materialbased upon the signals produced by the electromagnetic sensor and theacoustic detector.

According to another aspect, a material property gauge may include anelectromagnetic sensor operable to measure a response of constructionmaterial to an electromagnetic field and operable to produce a signalrepresenting the measured response by the construction material to theelectromagnetic field. Further, the gauge may include a temperaturesensor operable to measure a temperature associated with theconstruction material and operable to produce a signal representing themeasured temperature associated with the construction material. Amaterial property calculation function may be configured to calculate aproperty value associated with the construction material based upon thesignals produced by the electromagnetic sensor and the temperaturesensor.

As used herein, the terms “sample construction material,” “samplematerial,” and “construction material” refer to any suitable materialused in a construction process. Exemplary sample construction materialsinclude soil, asphalt, pavement, stone, sub-base material, sub-gradematerial, cement, agricultural soils, batch plants, concrete curingrate, concrete chloride inclusion, sodium chloride content, concretedelamination, water content, water-cement materials, alkali-silica,various soils, flexible asphalt, and any combination thereof.

As used herein, the terms “electromagnetic field generator” and“electromagnetic field source” refer to any suitable device or componentoperable to generate an electromagnetic field. Exemplary electromagneticfield generators include a voltage controlled oscillator (VCO), a Clapposcillator, a relaxation oscillator, a ring oscillator, an RCoscillator, a crystal oscillator, a blocking oscillator, a phase-lockedoscillator, a voltage oscillator, a multivibrator, a Gunn diode, anumerically-controlled oscillator, a Kystron tube, a high-powermicrowave magnetron, a backward wave oscillator, a VLF transmitter, anintegrated circuit timer, an arbitrary waveform generator, a pulse-widemodulation device, an analog synthesizer, current sources, synthesizedsources, YIG-tuned oscillators, and integrated circuits.

As used herein, the terms “acoustic generator” and “acoustic source”refer to any suitable device or component operable to generate acousticenergy. Exemplary acoustic generators include a penetrometer, a CleggHammer, a falling weight deflectometer, a Briaud compaction device, andan FWD, a geophone, an accelerometer, a vibration sensor, apiezoelectric device, an inductive coil-based device, a magnetostrictivedevice, a bender element, and micro-electro-mechanical system(MEMS)-based device electromechanical shakers, solenoid activatedhammers, instrumented hammers, frequency domain devices, and time domaindevices.

The subject matter described herein may be implemented using a computerprogram product comprising computer executable instructions embodied ina computer-readable medium. Exemplary computer-readable media suitablefor implementing the subject matter described herein include chip memorydevices, disk memory devices, programmable logic devices, applicationspecific integrated circuits, and downloadable electrical signals. Inaddition, a computer-readable medium that implements the subject matterdescribed herein may be located on a single device or computing platformor may be distributed across multiple devices or computing platforms.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the subject matter described herein will now beexplained with reference to the accompanying drawings of which:

FIG. 1A is a vertical cross-sectional view of a material property gaugefor measuring the density or modulus of material according to anembodiment of the subject matter described herein;

FIG. 1B is a schematic diagram illustrating a use of an exemplaryacoustic source and an exemplary acoustic detector for determining adensity and modulus of a sample material;

FIG. 1C is schematic diagram illustrating use of an exemplary acousticsource and an exemplary acoustic detector for determining a density andmodulus of a sample material;

FIG. 1D is a schematic diagram of an exemplary material property gaugeincluding a moisture sensor, a pair of acoustic detectors, an acousticgenerator, and a penetrometer according to one embodiment of the subjectmatter described herein;

FIG. 2A is a vertical cross-sectional view of material property gaugeshown in FIG. 1A configured in a backscatter mode for measuring thedensity or modulus of asphalt according to an embodiment of the subjectmatter described herein;

FIG. 2B is a graph of exemplary time domain waveforms as detected byaccelerometer;

FIG. 2C is a graph of exemplary frequency domain signals with respect tocoherence, phase, and magnitude;

FIG. 2D is a graph showing a moisture-modulus curve;

FIG. 2E is a graph showing modulus variations versus moisture contentfor the same sample material tested with respect to FIG. 2D;

FIG. 3 is a vertical cross-sectional view of an instrumented dynamiccone penetrometer according to an embodiment of the subject matterdescribed herein;

FIG. 4 is a vertical cross-sectional view of a material property gaugeincluding a rod with electrical components integrated therein for use inmeasuring material sample properties according to an embodiment of thesubject matter described herein;

FIG. 5 is a partial vertical cross-sectional view of a portable seismicpavement analyzer (or material property gauge) including acoustic andelectromagnetic components positioned on a bottom surface of the gaugeaccording to an embodiment of the subject matter described herein;

FIG. 6 is a graph showing the linear relationship between variations ofa construction mix's void percentage and modulus;

FIG. 7 is a graph showing the relationship between variations of asphalttemperature and modulus;

FIG. 8 is a top perspective view of a microwave moisture meter for usein material property gauges according to the subject matter describedherein;

FIG. 9 is a graph showing frequency variations with respect to moisturecontent;

FIG. 10A is a vertical cross-sectional view of an exemplary lowerfrequency fringing sensor;

FIG. 10B is a vertical cross-sectional view of another exemplary lowerfrequency fringing sensor;

FIG. 11A is a graph showing a comparison of dielectric constants of claymaterial (cohesive soil) and non-clay material (non-cohesive soil) overdifferent frequencies;

FIG. 11B is a graph showing the dielectric dispersion of theconductivity and dielectric constant of a cohesive soil;

FIG. 11C is a graph showing dielectric constant dispersion of severaldifferent types of clays;

FIG. 12 is a schematic diagram of an exemplary material property gaugeincluding acoustical impedance and electrical impedance functionalityaccording to an embodiment of the subject matter described herein;

FIG. 13 is a flow chart of an exemplary process for propertymeasurements using gauge shown in FIGS. 1A and 1B configured in atransmission mode or a backscatter mode according to an embodiment ofthe subject matter described herein;

FIG. 14 is a flow chart illustrating an exemplary process for propertymeasurements using gauge shown in FIGS. 1A and 1B for surface analysisaccording to an embodiment of the subject matter described herein;

FIG. 15 is a flow chart of an exemplary process for measuring soilmodulus according to an embodiment of the subject matter describedherein;

FIG. 16 is a flow chart of an exemplary process for measuring asphaltmodulus according to an embodiment of the subject matter describedherein;

FIG. 17 is a block diagram showing operation of a material propertygauge according to an embodiment of the subject matter described herein;

FIG. 18 is a block diagram showing operation of a material propertygauge according to an embodiment of the subject matter described herein;and

FIG. 19 is a flow chart illustrating an exemplary process forcalculating a property value of a construction material according to anembodiment of the subject matter described herein.

DETAILED DESCRIPTION

The subject matter described herein includes methods, systems, andcomputer program products for determining a property of constructionmaterial and/or various other materials. In one embodiment, the methods,systems, and computer program products described herein may determine aproperty value associated with a construction material under test.Exemplary construction materials include asphalt, soil, concrete,aggregate, and the like. Exemplary property values that may bedetermined include moisture content, Poisson ratio, modulus, shearstrength, density, void content, and the like. According to one aspect,a material property gauge may include an electromagnetic sensor operableto measure a response of construction material to an electromagneticfield. The electromagnetic sensor may produce a signal representing themeasured response by the construction material to the electromagneticfield. An acoustic detector may detect a response of the constructionmaterial to acoustical energy. Further, the acoustic detector mayproduce a signal representing the detected response by the constructionmaterial to the acoustical energy. A material property calculationfunction configured to calculate a property value associated with theconstruction material based upon the signals produced by theelectromagnetic sensor and the acoustic detector. In one example, amaterial property calculation function may use a moisture contentmeasurement for correcting determined property values of constructionmaterial.

Another important factor affecting the modulus of construction materialincludes temperature, particularly with asphalt. In another embodimentof the subject matter described herein, material property gauges andrelated methods are provided for using temperature measurements inmaterial property calculations, particularly for making corrections todetermined property values of construction material. According to oneaspect, a material property gauge may include an electromagnetic sensoroperable to measure a response of construction material to anelectromagnetic field. The electromagnetic sensor may produce a signalrepresenting the measured response by the construction material to theelectromagnetic field. A temperature detector may correct a response ofthe construction material to acoustical or electromagnetic energy. Amaterial property calculation function configured to calculate aproperty value associated with the construction material based upon thesignals produced by the electromagnetic sensor and the temperaturedetector.

In one example of a property of interest in road constructionengineering, mechanistic design methods characterize pavement based onits elastic response to a vehicular load. In this example, the pavementstructure may be composed of asphaltic material or concrete surface,base, and subgrade, each having a material thickness t and characterizedby the elastic modulus E, Poisson ratio v, and aggregate interfacefriction f. This results in a layered elastic system that can beanalyzed using engineering mechanics. As a result, design andperformance can be estimated from computations or measured stress andstrains on each layer resulting in a systematic design and predictedresponse from the surface.

Mineralogy, degree of saturation, void ratio, gradation, texture, andsoil fabric have important effects on the strength or modulus of soil.Further, for flexible pavements, the asphalt content, voids filled withasphalt (VFA), voids in mineral aggregate (VMA), binder modulus,temperature, and frequency of the load affect the modulus of theasphalt. The nuclear-based and electromagnetic-based measurements may beused for calculating the asphalt content, voids in surface pavement,moisture ratio of soil, and void ratio of soil. These volumetricparameters are related to the elastic response of a soil, asphalt, orpavement structure.

In one embodiment, the material property gauges according to the subjectmatter described herein may comprise an integrated and portable device.Further, the material property gauges may be operable in either in abackscatter mode or in both a backscatter mode and a transmission mode,as described in further detail herein. In one example of a gauge capableof transmission mode, the gauge may include a radiation source that isvertically moveable from a backscatter position, where it resides withinthe gauge housing, to a series of transmission positions, where it isinserted into holes or bores in the sample material. Nuclear gaugescapable of measuring the density of sample materials have been developedby the assignee of the present subject matter. For example, nucleargauges for measuring the density of sample materials are disclosed inU.S. Pat. Nos. 4,641,030; 4,701,868; and 6,310,936, all of which areincorporated herein by reference in their entirety.

FIG. 1A is a vertical cross-sectional view of a material property gauge100 for measuring the density or modulus of material according to anembodiment of the subject matter described herein. Gauge 100 is operableto accurately determine a property value of a construction material,such as soil, asphalt, or any other suitable construction and/or pavingmaterial. Exemplary property values that may be determined by gauge 100include mechanistic values, volumetric values, and moisture contentvalues. Gauge 100 may measure a property value of soil in a transmissionmode and measure a property value of asphalt in a backscatter mode.Gauge 100 has multi-functional use in that, with proper calibration, thegauge may be used for the in-situ measurements of moisture and density(and moisture and modulus) of construction materials, such as soils,asphalt, concrete, and the like.

Referring to FIG. 1A, gauge 100 is shown in a transmission mode, inwhich a tip end 102 of penetrometer 104 is positioned in an interior ofa construction material 106. Penetrometer 104 may be adapted forgenerating acoustical energy in the interior of construction material106 for detection of a response by construction material 106 to theacoustical energy. An operator of gauge 100 may manually generate theacoustical energy by moving an end 108 of penetrometer 104 distal tipend 102 in a vertical downward direction (indicated by direction arrow110) towards the interior of construction material 106. Penetrometer end108 may include a knob 112 for grip by the operator. A hammer component114 may be fixedly attached to penetrometer end 108 such that themovement of component 114 corresponds to the movement of penetrometerend 108.

An acoustic anvil component 116 may be fixedly attached to tip end 102.Anvil component 116 and tip end 102 may be fixed with respect to gaugehousing 118 in the transmission mode. Further, penetrometer end 108 andhammer component 114 may freely move with respect to anvil component 116and tip end 102 such that a bottom surface 120 of hammer component 114may contact a top surface 122 of anvil component 116 to generateacoustical energy. The acoustical energy may propagate the length ofpenetrometer 104 to tip end 102. The generated acoustical energy mayalso propagate into construction material 106.

In one embodiment, a penetrometer may be integrated into the gauge thatincludes a dual mass hammer. The dual mass hammer may include a firsthammer of large mass for use in initial penetration of constructionmaterial. Further, the dual mass hammer may include a second hammer ofsmaller mass for use in generating an acoustical disturbance. Otherexemplary devices for use with a penetrometer to generate acousticalenergy include piezoelectronic sources, shakers, bender elements, andthe like.

Gauge 100 may include one or more acoustic detectors 124 and 126operable to detect the response of construction material 106 to theacoustical energy and operable to produce one or more signalsrepresenting the detected response by construction material 106 to theacoustical energy. In particular, acoustic detector 124 may be anaccelerometer or geophone adapted for detecting acoustical energypropagating in a vertical direction. Acoustic detector 126 may be anaccelerometer or geophone adapted for detecting acoustical energypropagating in a horizontal direction. Accelerometers are available by,for example, Endevco Corporation, of San Juan Capistrono, Calif.

The acoustical energy detected by acoustic detectors 124 and 126 may beacoustical energy produced by construction material 106 in response tothe acoustical energy produced by penetrometer 104. Acoustic detectors124 and 126 may be capable of wide band frequency response from severalhertz to 100 kHz. In response to detecting acoustical energy, acousticdetectors 124 and 126 may generate electrical signals representing theacoustical energy and communicate the electrical signals to a printedcircuit board (PCB) 128 configured to process the electrical signalsand/or store data representative of the detected acoustical energy.Further, PCB 128 may include hardware, software, and/or firmwarecomponents suitable for receiving, processing, and transmittingelectrical signals and suitable for storing data representative ofvalues represented by the electrical signals. PCB 128 may communicateelectrical signals representative of the detected acoustical energy toanother PCB 130 for further processing and for use in determining aproperty value associated with construction material 106, as describedin further detail herein.

FIGS. 1B and 1C are schematic diagrams illustrating the use of anacoustic source and an acoustic detector for determining a density andmodulus of a sample material. Referring to FIG. 1B, an acoustic source156 may be inserted into a sample material 158 to a known depth by apenetrometer 160. Acoustic energy may travel a path 162 to an acousticdetector 164. The time of flight for the acoustic energy may bedetermined based on initiation of the acoustic energy by penetrometer160 and the time that the acoustic energy is detected at detector 164.Further, the distance of path 162 may be estimated based on the knowndepth and the distance between the penetrometer entry point on thesurface of sample material 158 and the position of detector 164. Thedistance of path 162 and time of flight data may be used for estimatinga phase velocity. Based on elastic theory, the phase velocity can beused for determining a density and modulus of sample material 158.

Referring to FIG. 1C, in a similar manner to the system shown in FIG.1B, the system shown in 1C includes an acoustic source 166 for directingacoustical energy into a sample material 168, and an acoustic detector170 for detecting the response of sample material 168 to the acousticalenergy. Further, a density or modulus of sample material 168 may bedetected based on a path distance between source 166 and detector 170and a determined time of flight of the acoustical energy. The system ofFIG. 1C is different than the system shown in FIG. 1B in that acousticdetector 170 is positioned at an end of a penetrometer 172 and acousticsource 166 is positioned at a surface of sample material 168.

FIG. 1D illustrates a schematic diagram of an exemplary materialproperty gauge 174 including a moisture sensor 176, a pair of acousticdetectors 178 and 180, an acoustic generator 182, and a penetrometer 184according to one embodiment of the subject matter described herein.Referring to FIG. 1D, acoustic generator 182 may generate acousticalenergy, which is transmitted to a 600 cone tip end 186 of penetrometer184. In this example, acoustic generator 182 is rigidly affixed to ametal ring 188, which is affixed to penetrometer 184. The acousticalenergy may emit from tip end 186 into a sample material 190 and bereceived by detectors 178 and 180 for use in sample material propertyvalue calculations by an MPC 190. The data may be used for densitycalculations or modulus calculations. Exemplary acoustic generatorsinclude magnetostrictive elements, piezoelectric-based devices,electrodynamic devices, and micro-electro-mechanical systems(MEMS)-based devices. Further, suitable acoustic generators includebender elements produced by GDS Instruments, of London, United Kingdom.Another exemplary acoustic generator includes a device havingpiezoelectric materials positioned between materials that bend uponexcitement from the piezoelectric materials, magnetostrictive materialsand the like.

Further, moisture sensor 176 may be operable to detect a moisturecontent of sample material 190. Data representing the detected moisturecontent may be communicated to an MPC 192. The moisture content data maybe used for correcting density calculations.

Referring again to FIG. 1A, gauge 100 may include an electromagneticsensor 132 operable to measure a response of construction material 106to an electromagnetic field and operable to produce an electrical signalrepresentative of the measured response by construction material 106 tothe electromagnetic field. For example, electromagnetic sensor 132 maybe operable to measure a permittivity, resistivity, a dielectricconstant, and/or a conductivity of sample material 106.

In this example, gauge 100 may include an electromagnetic field source134 operable to generate an electromagnetic field and be positioned neara surface of construction material 106 such that the electromagneticfield extends into construction material 106. Alternatively, signalsource 134 and/or sensor 132 may be positioned within an interior ofsample material 212. In one embodiment, gauge 100 may include acomponent operable in a self-impedance mode, wherein terminal impedanceof the component is measured as it is powered, and the terminal ordriving point impedance changes as the permittivity increases.

Electromagnetic sensor 132 may detect at least a portion of theelectromagnetic field from construction material 106 that was producedby signal source 134. A frequency and/or time domain technique may beused for determining a property value of construction material 106. Theelectromagnetic field may range from static (DC) to microwave. Exemplaryfrequency techniques for use in determining a moisture property includeusing fringing field capacitors to produce an electromagnetic field;time domain reflectometry techniques; single-frequency techniques;sweeping-frequency techniques; microwave absorption techniques; andmicrowave phase shift techniques. Further, suitable moisture signaldetectors include detectors operable to measure the real and imaginaryparts of a dielectric constant at a single frequency, multiplefrequencies, continuous sweeps of frequencies, and/or chirps offrequency content. In the time domain, direct steps or pulses may beproduced by a signal source and detected by a detector for determining aproperty value. Further, a fast Fourier transform (FFT) technique may beapplied to the frequency and time domains for determining a propertyvalue. Further, an orthogonal or bi-orthogonal basis decompositiontechnique may be applied to the frequency and time domains (such as afast Fourier transform (FFT), wavelet transform, or wave-packetdecomposition) for determining a property value. The conductivity andpermittivity of construction material 106 may be determined based on thedetected electromagnetic field. In one example, the conductivity andpermittivity may be used for determining a moisture property ofconstruction material 106.

Gauge 100 may include a source window 136 and a receiver window 138associated with source 134 and sensor 132, respectively. Source window136 and receiver window 138 may extend through a base plate 140 suchthat electromagnetic fields may pass through base plate 140 and betweensource 134 and sensor 132. Exemplary window materials include aluminumoxide, sapphire, ceramics, plastics, and suitable insulators.

Another electromagnetic sensor 143 may be positioned within penetrometer104 for detecting an electromagnetic field of construction material 106.Sensor 143 may be positioned near end 102 of penetrometer 104 such thatsensor 143 is positioned within construction material 106 in thetransmission mode. In one example, sensor 143 may be a capacitancesensor operable to measure a moisture property of construction material106 at a predetermined depth with respect to the top surface ofconstruction material 106. Sensor 143 may communicate an electricalsignal representative of the measurement to PCB 130 for processing anduse in determining a property value associated with constructionmaterial 106.

A PCB 141 may be in operable communication with source 134 and sensor132. PCB 141 may include suitable hardware, software, and/or firmwarecomponents for control of source 134 and sensor 132. In particular, PCB141 may control source 134 to generate an electromagnetic field. Forexample, PCB 141 may supply power to circuitry of source 134 forgenerating a predetermined electromagnetic field. Further, PCB 141 maybe operable to receive a signal from sensor 132 representing detectedelectromagnetic fields via a coaxial cable 143. In one example, PCB 141may determine a moisture property of sample material 106 based on thesignal representation.

In one embodiment, a moisture property may be measured by operating adevice to perform a frequency sweep on a microwave moisture meter (e.g.,the meter shown in FIG. 8 and described herein). The moisture meter mayoperate in a self-impedance mode, wherein a complex terminal impedanceis measured at the input of a dipole. In one example, the dipoleresonates at 2.45 Ghz, at a resonance frequency where the return loss ofthe antenna is minimized. As water content increases, the dielectricconstant of the sample material increases, and thus increases theelectric field near field energy, thus reducing resonance.

Moisture measurement may rely on single variable or multi-variableequations. For example, water may be detected using one variable such asthe relative dielectric constant ε_(r). Interfacial polarization is animportant property response for heterogeneous materials. Because ofthese polarization effects (also referred to as Maxwell-Wagner effects),a resonance is produced in the permittivity spectrum. This relaxationmay be used for water content determination for a particular type ofsoil. At lower frequencies, the measured dielectric constant has theeffects of the Maxwell-Wagner phenomenon, thus leading to errors in thewater content measurement, which are also a function of temperature.Other exemplary variable include conductivity, permittivity, and thedispersion of the change in conductivity and the change of permittivitywith frequency. Further, for example, the relaxation frequency of somesoils is on the order of 27 Mhz. Further, the relaxation frequency ofsome soils is on the order of 10 MHz. Additional discussion is providedin U.S. patent application Ser. No. 10/971,546, filed Oct. 22, 2004(U.S. Patent Application Publication No. 2005/015028), commonlyassigned, and the disclosure of which is incorporated herein byreference in its entirety.

In one example, the capacitance of a fringing field detector is measuredusing a feedback loop in an oscillator circuit. The frequency isprovided by the following equation (wherein C_(eff) represents theeffective capacitance including the surrounding medium, parasitics inthe circuitry, and nominal capacitances in the tank circuit, and Lrepresents the inductance):2πF=1/(sqrt(LC _(eff)))The ratio between a reference frequency and the frequency with thefringing field capacitor switched in or included may be calibratedagainst moisture. The sensitivity of the measurement at thesefrequencies due to salt concentrations should be considered. The endresult is that chemical composition errors must be corrected, leading tomany different calibration curves for the soil types. Further,discussion is provided, for example, in U.S. Pat. Nos. 4,924,173;4,929,885; and 5,260,666, each of which are incorporated herein byreference in their entireties.

Microwave-based moisture property detectors may be advantageous, forexample, because such detectors can perform density-independent moisturemeasurements and are much less susceptible to chemical compositionerrors than their lower frequency counterparts. Such detectors may beadvantageous over neutron-based moisture property detectors, becauseneutron-based detectors are density and material dependent. Further, itis desirable to reduce the use of neutron sources because of U.S.Nuclear Regulatory Commission (NRC) regulations and fees associated withneutron sources.

Gauge 100 may include a temperature sensor 142 operable to measure atemperature associated with construction material 106. Further,temperature 142 may be in communication with temperature circuitry 144for producing an electrical signal representative of the measuredtemperature associated with construction material 106. Temperaturesensor 142 may be positioned near or at a surface of constructionmaterial 106 when base plate 140 of gauge 100 is positioned on thesurface of construction material 106 as shown in FIG. 1A. Exemplarytemperature sensors include infrared heat sensors, optical infraredsensors, resistance temperature detectors (RTDs), thermocouples, solidstate-based temperature sensors, and resistive-based temperaturesensors.

PCB 130 may be operable to receive one or more of the electrical signalsproduced by PCB 128, 141, and temperature circuitry 144 for determininga property value associated with construction material 106. Further, PCB130 may include an electromagnetic measurement manager 146 forreceiving, managing, and processing electrical signals representative ofelectromagnetic fields. PCB 141 may be operable to communicate tomanager 146 electrical signals representative of the detectedelectromagnetic fields. Manager 146 may include functionality forstoring data related to the detected electromagnetic fields.

Another temperature sensor 147 may be positioned in a “downhole”configuration in the interior of penetrometer end 102. Temperaturesensor 147 may be operable to measure a temperature associated with aninterior of construction material 106 in a gauge transmission mode. Anelectrical signal representative of the measured temperature associatedwith the interior of construction material 106 may be communicated toPCB 130 for use in determining a property value associated withconstruction material 106.

An acoustical measurement manager 148 may be operable to receive,manage, and process electrical signals representative of acousticalenergy. PCB 128 may be operable to communicate to manager 148 electricalsignals representative of the detected acoustical energy. Manager 148may include functionality for storing data related to the detectedacoustical energy.

A temperature measurement manager 150 may be operable to receive,manage, and process electrical signals representative of temperature.Temperature circuitry 144 may be operable to communicate to manager 150electrical signals representative of the detected temperatures. Manager150 may include functionality for storing data related to the detectedtemperatures.

As described in further detail herein, a material property calculationfunction (MPC) 151 may receive data from managers 146, 148, and 150regarding detected electromagnetic fields, acoustical energy, andtemperatures associated with construction material 106. Further, MPC 151may receive measurement data from sensor 143. The data may be used byMPC 151 for determining a property value of construction material 106.MPC 151 may include computer program instructions to determine theproperty value by using a portion or all of the data provided bymanagers 146, 148, and 150. For example, the data may be used forestimating a density of construction material 106 and/or correcting adensity estimation of construction material 106. MPC 151 may beprogrammed with the equations and data described herein for estimatingor determining the property value.

Further, MPC 151 may include suitable hardware, software, and/orfirmware components for implementing measurement and calibrationprocedures according to the subject matter described herein. MPC 151 mayinclude one or more processors and memory components. Exemplary MPCcomponents include one or more of pre-amplifiers, spectroscopic gradeGaussian amplifiers, peak detectors, and analog-to-digital converters(ADCs) for performing the processes described herein. Procedure status,feedback, and density measurement information may be presented to anoperator via one or more interfaces of gauge 100.

Gauge 100 may include an interface for receiving operator input and fordisplaying output to the operator. In particular, gauge 100 may includea display 152 for displaying output and a keypad 154 for receivingoperator input. A calculated property value of construction material 106may be displayed to an operator via display 152.

FIG. 2A is a vertical cross-sectional view of material property gauge100 shown in FIG. 1A configured in a backscatter mode for measuring thedensity or modulus of asphalt 200 according to an embodiment of thesubject matter described herein. Referring to FIG. 2A, in thebackscatter mode, penetrometer 104 may be in a position that is raisedwith respect to the transmission mode such that end 102 is positioned ona surface 202 of asphalt 200. An accelerometer 204 may be positioned inthe interior of end 102 for detecting acoustical energy from surface202. Acoustical energy may be propagated to asphalt 200 by acousticalsources positioned on a surface, such as at the locations of acousticdetectors 124 and 126. The response of asphalt 200 to the acousticalenergy may be detected by accelerometer 204 for analysis, the acousticalenergy of which may be generated from a component internal to gauge 100or another source. In another example, penetrometer 104 may transmitacoustical energy into asphalt at end 102, and detected by accelerometer204, acoustic detector 124, and/or acoustic detector 126 as the energyleaves end 102. Any of accelerometer 204 and acoustic detectors 124 and126 may be used for triggering from detected acoustic energy generatedby a component of gauge 100.

Further, accelerometer 204 may communicate an electrical signalrepresentative of the acoustical energy to PCB 130 for processing anduse in determining a property value associated with asphalt 200. Forexample, the data carried by the signal may be used for determining thedensity of asphalt 200. The data may be used alone or in combinationwith any of the other data detected by components of gauge 100. Forexample, the acoustical energy data may be combined with temperaturemeasurements by temperature sensor 142 for determining a density ormodulus of asphalt 200. In one example, penetrometer 104 is operable ofexciting impulse or swept frequency waves into sample material 200 to bereceived by at least one of acoustic detectors 124 and 126. Modulus anddensity may be determined based on surface waves.

FIG. 2B is a graph illustrating exemplary time domain waveforms asdetected by accelerometer 204. In this example, the acoustical energy isinitiated at in the surface of a sample material by an impact at thelocations of acoustic detectors 124 and 126. The two traces representthe X and Y directional sensors of triaxial accelerometer 204 in thehorizontal and vertical directions, respectively. The acoustical energypropagates radially from the locations towards accelerometer 204 fordetection. The wave indicated by P is detected by accelerometer 204before the wave indicated by S.

FIG. 2C is a graph illustrating exemplary frequency domain signals withrespect to coherence, phase, and magnitude. A coherence function may beused to obtain the quality of a signal. If the coherence issubstantially less than 1, the measurement attempt is rejected. Afterabout 5 good averages, the cross-power spectrum may be used to obtainphase and amplitude spectra.

An exemplary technique for the spectral analysis of surface waves (SASW)is described by Nazarian and Stoke in the publication “NondestructiveEvaluation of Pavement by Surface Wave Methods” (ASTM 1026, 1989), and“Nondestructive Testing of Concrete Structures Using the Rayleigh WaveDispersion Method”, by N. Krstulovic-Opara, R. Woods, N. Al-Shayea (ACMaterials Journal, pp. 75-86, vol. 93, no. 1, 1996), and U.S. Pat. Nos.5,614,670; and 5,095,465, the disclosures of which are incorporatedherein by reference in their entireties. This technique measures thedispersive properties of the surface waves. By examining the phasevelocity as a function of frequency or wavelength and using an inversionprocess, sample material properties as a function of thickness may beobtained. In use, the transfer and coherence functions between acousticdetectors may be determined. Further, the dispersion curve may beautomatically assembled through the use of cross power spectrum andcoherence functions. Analysis of the dispersion curve may yield themodulus of different layers of sample material.

Another exemplary technique similar to SASW is known as the ultrasonicsurface wave method. In this technique, only a top layer of samplematerial is analyzed as the frequencies are much higher and wavelengthson the order of the surface thickness. As a result, complex numericalanalysis for back calculation of desired values is not necessary and theproperties may be directly determined. The following equation may beused for determining shear modulus (where ρ represents mass density, vrepresents Poisson ratio, D represents the distance between acousticdetectors, and m represents the slope of the phase response in thetransfer function between acoustic energy source and the acousticdetectors):G=ρ[(1.13−0.16v)(m/D*360)]²In this approach, for operational modes of the gauges described herein,the Poisson ratio is either assumed or measured by the ratio of the Pand S wave velocities. Further, the density may be determined orestimated according to the subject matter described herein.Alternatively, density may be determined by drill core sampling andlaboratory testing based on Archimedes principles. An exemplary surfacewave detector is described in U.S. Pat. No. 5,095,465, the disclosure ofwhich is incorporated herein in its entirety. Time and frequency domaintechniques may be used for calculating phase velocity, or for resonatingacoustical waveguide structures with reflection and transmissionanalysis.

Variations in moisture content of a sample material can significantlyaffect modulus. The material property gauges described herein mayinclude functionality for correcting for moisture content variations inmodulus calculations. For base construction materials such as soils, themodulus may be related to one of the construction parameters such asmoisture. By performing a Proctor-like test, the optimummoisture-modulus curve may be obtained and are useful for calibrationpurposes. FIG. 2D is a graph showing a moisture-modulus curve. As shownin the graph, the optimum moisture content is about 6%. FIG. 2E is agraph showing modulus variations versus moisture content for the samesample material tested with respect to FIG. 2D. By fitting a polynomialfunction to this response and incorporating the fitted polynomialfunction into a field calibration, the field modulus of a samplematerial may be estimated as a function of moisture content.

In operational modes of the gauges described herein, dispersion may bedetermined by calculating phase velocity as a function of wavelengthusing the distance between acoustic detectors, or in the case of oneacoustic detector, the distance between the acoustic source and the oneacoustic detector. The following equation may be used for calculatingthe phase velocity (wherein f represents frequency, D represents thedistance in meters, X represents the wavelength in meters, and θrepresents the phase in radians):V _(R)(λ)=2πfD/θ

SASW or ultrasonic surface wave techniques may be integrated into thefunctionality of a material property measurement gauge as describedherein. The equations may be programmed into an MPC and data obtained bygauge component detection for determining a property value of the samplematerial.

For flexible pavements, empirical models may be used for calculating themodulus of a sample material as a function of volumetric properties suchas asphalt content, void ratio, binder viscosity, temperature, and mixdesign. For example, the following equation was determined by Witczakand reported in the publication “Typical Dynamic Moduli for NorthCarolina Asphalt Concrete Mixtures” by Y. R. Kim, M. Momen, and M. King(Final Report, FWHA/NC 2005-03):${\log{E^{*}}} = {{- 1.2499379} + {0.029232 \cdot p_{200}} - {0.001767 \cdot \left( p_{200} \right)^{2}} - {0.002841 \cdot p_{4}} - {0.058097 \cdot V_{a}} - {0.802208 \cdot \frac{{Vb}_{eff}}{\left( {{Vb}_{eff} + V_{a}} \right)}} + \frac{\begin{matrix}{{3.871977\quad - \quad{0.0021 \cdot \quad p_{\quad 4}}\quad + \quad{0.003958 \cdot \quad p_{\quad 8}}\quad -}\quad} \\{{0.000017 \cdot \quad\left( \quad p_{\quad 38} \right)^{2}}\quad + \quad{0.005470 \cdot \quad p_{\quad 34}}}\end{matrix}}{1 + {\mathbb{e}}^{({{- 0.603313} - {0.313351 \cdot {\log{(f)}}} - {0.393533\quad{\log{(\eta)}}}}}}}$where |E*|=the asphalt mix dynamic modulus in 10⁵ psi;

η=bittimen viscosity in 10⁶ poise (at any temperature, degree of aging);

f=load frequency in Hz,

V_(a)=% air voids in tie mix, by volume;

Vb_(eff)=% effective bitumen content, by volume;

P₃₄=% retained in the ¾ in. sieve, by total aggregate weight(cumulative);

P₃₈=% retained in the ⅜ in. sieve, by total aggregate weight(cumulative);

P₄=% retained in the No. 4 sieve, by total aggregate weight(cumulative); and

P₂₀₀=% passing the No. 200 sieve, by total aggregate weight.

Further, the Hirsch model was developed for estimating the dynamicmodulus of flexible pavement based on VMA, VFA, and binder modulus. Themodel is based on the law of mixtures for different phases of a materialjoined in series and parallel cells. The Hirsch model is represented bythe following equation:$E^{*} = {{P_{c}\left\lbrack {{4200000\left( {1 - {{VMA}/100}} \right)} + {3{G^{*}}\left( \frac{{VFA} \times {VMA}}{10000} \right)}} \right\rbrack} + {\left( {1 - P_{c}} \right)\left\lbrack {\frac{1 - {{VMA}/100}}{4200000} + \frac{VMA}{3{VFA}{G^{*}}}} \right\rbrack}^{- 1}}$where${P_{c} = {\frac{\left( {20 + \frac{{VFA} \times 3{G^{*}}}{VMA}} \right)^{0.58}}{650 + \left( \frac{{VFA} \times 3{G^{*}}}{VMA} \right)^{0.58}} = {{aggregate}\quad{contact}\quad{volume}}}};$

VFA=voids filled with asphalt;

VMA=voids in mineral aggregate; and

|G*|=dynamic shear modulus of binder.

By incorporating these models and equations into calculations performedby gauges according to the subject matter described herein, estimates ofdynamic modulus may be obtained. Other suitable prediction models may beincorporated as well.

FIG. 3 illustrates a vertical cross-sectional view of an instrumenteddynamic cone penetrometer (IDCP) 300 according to an embodiment of thesubject matter described herein. Penetrometer 300 may be integrated intoa gauge such as gauge 100 (shown in FIGS. 1 and 2). Data obtained bypenetrometer 300 may be communicated to an MPC, such as MPC 151 shown inFIGS. 1 and 2), for use in determining a property value of aconstruction material. Referring to FIG. 3, penetrometer 300 may includea hammer component 302 and an anvil component 304 adapted for movementwith respect to one another such that the components can impact with aforce for producing acoustical energy into a construction material.Hammer component 302 may have a mass of about 1 kilogram. Penetrometer300 may include a force transducer 306 operable to measure the contactforce between components 302 and 304. An electrical signal representingthe measured contact force may be communicated to the MPC via wire 308for use in property value calculations.

Penetration resistance refers to the number of hammer impacts permillimeter. In one example, a force transducer may count the number ofimpacts, and the accelerometer may integrate to find the distance ofpenetration. In another example, by storing data about the force andacceleration of an anvil, energy may be measured using the followingequation:E=∫F(t)V(t)dtThe distance or displacement of a tip end or cone end of a penetrometerinto a construction material may be found by integrating theacceleration twice with respect to time. The soil resistance refers tothe work done by the soil to stop the movement of the penetrometer tipend divided by the distance the penetrometer travels, which may beexpressed using the following equation (wherein R represents the soilresistance, X represents the distance of travel with each impact of thehammer, and W represents the work equal to the change of kineticenergy=½ mV² with V being the final velocity striking the anvil toresult from the earth's gravitational acceleration of 9.8 m/s²):R=W/X

Further, penetrometer 300 may include a 3-axis accelerometer 310positioned in the interior of penetrometer end 311, the end ofpenetrometer 300 for positioning in the interior of a sample material.Detectors 124 and 126 may be operable to detect acoustical energy fromthe sample material. The detected acoustical energy may be theacoustical energy propagated to the sample material from contact ofcomponents 302 and 304. Further, from surface excitations originatingfrom detector 124 and/or detector 126, the response of the samplematerial to the acoustical energy may be detected by accelerometer 310.Further, accelerometer 310 may communicate an electrical signalrepresentative of the acoustical energy to the MPC for processing anduse in determining a property value associated with the sample material.The electrical signal may be communicated via a wire 312. For example,the data carried by the signal may be used for determining the densityor stiffness depth profile of the sample material. The data may be usedalone or in combination with any of the other data detected bycomponents of the gauge. For example, the acoustical energy data may becombined with moisture measurements by a moisture sensor for determininga moisture corrected soil modulus. Similarly, when end 311 is positionedon the construction material surface and excites acoustic waves towardsdetectors 124 and 126, the acoustical energy data may be used withtemperature measurements obtained by a temperature sensor fordetermining corrected asphalt modulus.

Penetrometer 300 may also include another accelerometer 314 attached toa bottom surface of anvil component 304. Accelerometer 314 may beoperable to determine a velocity and sample material penetrationdistance by driving penetrometer 300 into the soil and storing theassociated force and acceleration data. By twice integrating a signalobtained from accelerometer 314, the penetration distance may bedetermined. Further, accelerometer 314 may be operable to generate anelectrical signal representing the determined velocity and samplematerial penetration distance and communicate the signal to the MPC viaa wire 316 for use in calculating the penetration distance for eachhammer impact. The resistance may be used to form a soil density profileas a function of depth, which may be used by an MPC for calculating asoil density or modulus.

A moisture sensor 318 may be positioned near end 311 of penetrometer 300for placement in the interior of sample material. Moisture sensor 318may be operable to measure moisture content of the sample material. Anelectrical signal representing the measured moisture content may begenerated and communicated to the MPC via a wire 320. The measuredmoisture content may be used for determining a property value of thesample material. For example, the measured moisture content may be usedto correct density measurements determined by other components of thegauge.

In one embodiment, multiple penetrometers may be used for obtainingacoustical measurements from different positions in the interior of asample material. In one configuration, acoustical energy may begenerated from the penetrometers. In another configuration, acousticalenergy generated from a surface may be received at the ends of thepenetrometers positioned in the sample material. The penetrometers maybe coaxially aligned and parallel.

Penetrometers may be positioned in a sample material in any suitablemanner such that the penetrating end of the penetrometer is tightlyfitted to the sample material. For example, a drill rod technique may beused for positioning a penetrometer in a sample material. In anotherexample, abrupt force may be applied to an end of penetrometer that isdistal the sample material penetrating end for forcing the penetrometerinto the sample material. An impact force may be applied, for example,by impacting an anvil component of the penetrometer with a hammercomponent. In this example, one or more accelerometers may be attachedto the penetrometer for measuring the velocity of the penetrometer'smovement and an impulse response of the sample material. Thisinformation may be used to determine a shear strength of the samplematerial simultaneously with the operation of the gauge. Other propertyvalues, such as density, of the sample material may be determined usingthe information. Similar techniques are described in the AmericanSociety of Testing and Materials (ASTM) standard D-4633 (known as thedynamic penetrometer test), the standard penetration test (SPT), andASTM standards D-5778, D-3441, and D-6187.

The acoustic energy response of a sample material may be determined byexamining the waves generated by the acoustic energy. In particular, forexample, an impulse excitation may be applied to a penetrometerpositioned in sample material as shown in FIG. 1A. Alternatively,impulse excitation may be applied to a top surface of the samplematerial. The impulse excitation may generate a disturbance in thesample material. Generally, the following two types of waves may begenerated by the disturbance: P waves and S waves. P waves exhibit apush-pull motion to particles of the sample material, such as soilparticles. S waves generate a motion that is transverse to the directionof propagation. The velocity of the P waves is higher than that of the Swaves. Thus, the P waves arrive at an acoustic detector prior to the Swaves.

The velocity of the waves may be found by dividing the distance betweenthe source of excitation (or acoustical energy) and the acousticdetector by the time for arrival of the wave. In the deep interior ofthe sample material, body waves associated with the bulk moduluspropagate. Table 1 below shows relationships between moduli and Poissonratio (wherein Vp represents compressional wave velocity, and ρrepresents mass density). TABLE 1 Moduli and Poisson Ratio RelationshipsLames Poisson Sheer Bulk Modulus Young's Modulus Constant Ratio ModulusK E λ μ ρV_(P) ² G $\lambda + \frac{2\quad G}{3}$ 2 ρV_(S) ²(1 + μ)$K - {\frac{2}{3}G}$ $\frac{\lambda}{2\left( {\lambda + G} \right)}$ λ +2 μ $\frac{E}{2\left( {1 + \mu} \right)}$$\frac{EG}{3\left( {{3\quad G} - E} \right)}$ 2 ρ(1 + μ)(1.35 −0.182μ)²V_(R) ² $G\quad\frac{E - {2\quad G}}{{3\quad G} - E}$$\frac{{3\quad K} - E}{6\quad K}$ 3 K − 2 λ$\frac{2}{3}\left( {K - \lambda} \right)$$\frac{E}{3\left( {1 - {2\quad\mu}} \right)}$$\frac{{{\rho V}_{P}^{2}\left( {1 + \mu} \right)}\left( {1 - {2\quad\mu}} \right)}{1 - \mu}$$\frac{2\quad{\mu G}}{1 - {2\quad\mu}}$$\frac{{3\quad K} - {2\quad\mu}}{2\left( {{3\quad K} + \mu} \right)}$$K + {\frac{4}{3}\mu}$ $\lambda\frac{1 - {2\quad\mu}}{2\quad\mu}$$G\frac{2\left( {1 + \mu} \right)}{3\left( {1 - {2\quad\mu}} \right)}$$\frac{G\left( {{3\quad\lambda} + {2\quad G}} \right)}{\lambda + G}$$3\quad K\quad\frac{{3\quad K} - E}{{9\quad K} - E}$$\frac{E}{2\quad\mu} - 1$ $\mu\frac{{4\quad\mu} - E}{{3\quad\mu} - E}$$3\quad K\frac{1 - {2\quad\mu}}{2 + {2\quad\mu}}$$\lambda\frac{1 + \mu}{3\quad\mu}$ 2 G(1 + μ)$3\quad K\quad\frac{\mu}{1 + \mu}$$\frac{1}{2}\frac{\left( \frac{V_{P}}{V_{S}} \right)^{2} - 2}{\left( \frac{V_{P}}{V_{S}} \right)^{2} - 1}$$3\quad K\frac{{3\quad K} + E}{{9\quad K} - E}$$\frac{3\quad{KE}}{{9\quad K} - E}$$\rho\left( {V_{P}^{2} - {\frac{4}{3}V_{S}^{2}}} \right)$ 3 K(1 − 2 μ)ρ(V_(P) ² − 2 V_(S) ²) $\lambda\frac{1 - \mu}{\mu}$ ρV_(S) ²$\frac{9\quad K{\quad\quad}\mu}{{3\quad K} + \mu}$$\mu\frac{2 - {2\quad\mu}}{1 - {2\quad\mu}}$$9\quad K\frac{K - \lambda}{{3\quad K} - \lambda}$$3\quad K\frac{1 - \mu}{1 + \mu}$$\lambda\frac{\left( {1 - \mu} \right)\left( {1 - {2\quad\mu}} \right)}{\mu}$$\frac{E\left( {1 - \mu} \right)}{\left( {1 + \mu} \right)\left( {1 - {2\quad\mu}} \right)}$

As stated above, the distance may be the distance between the tip end ofa penetrometer and the acoustic detector. The arrival time may bedetermined for both wave types. Once the velocity is determined, theshear wave modulus may be calculated using the mass density ρ in thefollowing equation:G=ρV _(s) ²Alternatively, if the Poisson ratio v is known, the following equationrelates Shear modulus to Young's modulus:E=2G(1+v)=2ρV _(s) ²(1+v)In general, the Poisson ratio links the two types of wave velocitiesthrough the equation (where α=V_(p)/V_(s)):v=(0.5α²−1)/(α²−1)Referring again to FIG. 2A, time domain traces from the two axes of anaccelerometer are shown. When the source is horizontally close to thez-axis of the penetrometer, the waves travel predominantly vertical withcompression-like characteristics. When the horizontal distance isincreased, the horizontal accelerometer is predominat with shear energy.In one exemplary application, the maximum horizontal distance was 50 cm.Using signal processing and a programmed computer program product, theproper rise time for both P and S waves may be selected.

Other exemplary techniques for determining an impulse response of asample material as a result of an impact are generally described by thepublication “An Impact Testing Device for In-Situ Base CourseEvaluation”, by B. Clegg (ARRB Proceedings, vol. 8, pp. 1-6,1976) andthe ASTM standards D-5874-02, D-1883, D-5874, D-2216, D-4959, andD-4643, the disclosures of which are incorporated by reference herein intheir entireties. A Clegg hammer is referred to a device operable tomeasure the impulse response of a soil halfspace as the result of ahammer impact. Further, for example, ASTM D-5874-02 describes a testmethod for determining the impact value (IV) of a soil. In the exemplaryASTM test method, a 4.5 kg mass is used for evaluating the strength ofan unsaturated compacted fill for pavement materials, soils,soil-aggregates having a maximum particle size less than 37.5 mm.Further, lighter hammers of about 0.5 kg mass are applicable for lowerstrength soils such as fine grained cohesionless, highly organic,saturated or highly plastic soils having a particle size less than 9.5mm. An accelerometer is attached to the hammer and peak of the responseis recorded. The stiffer the soil, the less elastic it is, and thegreater the de-acceleration. In use, the hammer is placed on thematerial either in the field or in a laboratory mold, raised to a fixedheight and released. An average of four blows is typical of a singlemeasurement. The impact value reflects and responds to changes in thesoil characteristics influenced by strength. This is a dynamicpenetration property similar to the California Bearing Ratio (CBR) test,the ASTM standard D-1883. According to ASTM standard D-5874, the methodprovides immediate results as a strength index value from which thequality of the fill may be inferred for the particular moistureconditions. This method also incorporates separate moisture measurementsas described by, for example, ASTM standards D-2216, D-4959, and D-4643,wherein the water is removed by thermal methods and calculated as apercent of dry material. The peak acceleration can be integrated oncefor velocity as a function of time, and again for distance orpenetration into the soil as a function of time.

Other exemplary techniques for determining the soil properties includecone penetrometer techniques. In a cone penetration test (CPT), a60-degree apex cone at the end of a series of rods is pushed into theground at a constant rate of 15-25 mm/s and continuous or intermittentmeasurements are made of the mechanical resistance to the penetration ofthe cone. A force is measured by means of a load cell just behind thecone. The force due to side friction is also measured directly above thecone using a sleeve in contact with the bore wall. Typical penetrationcones have a diameter of 37.5 mm and an apex angle of 60 degrees. Thetotal force Q as measured by strain gauges or other force sensorsdivided by the area A is the resistance q. The sleeve Force divided bythe cylindrical sleeve area is the sleeve friction coefficient f. Conepenetrometers are use to investigate the subsurface geological strata,groundwater conditions, and the physical and mechanical properties of asoil or sub-base, and to classify the material. Because the diameter ofthe penetrometer can be on the order of 50 mm, and they are pushed intothe soil at a constant rate, large rigs are normally used consisting ofhydraulic jacking and reaction systems producing forces of 10-20 tons.Hence, these are not portable systems. Such miniature systems may beincorporated into the subject matter describe herein. The electricalparameters are inferred from measurements from the voltage at constantcurrent across an electrode pair in contact with the soil. The formationfactor F is defined as the ratio of the resistivity of the soil and theresistivity of the pore fluid. The formation factor F is linked to soilporosity n by the following equation (wherein A and m representconstants found in laboratory calibrations of field samples):F=An ^(−m)Exemplary sensors that can be integrated into the CPT include

Temperature

Electrical resistivity

Dielectric spectroscopy

PH

Redox Potential

Gamma and Neutron sources/sensors

Laser Induced Fluorescence

IR or Optical cameras

Liquid Samplers

Vapor Samplers

Moisture sensors

Integrated Optics

Ramon Spectroscopy

Chemical Sensors

MEMs

Friction Sleeves

Pore water quality

Load cells

All of theses sensors could be used to analyze a soil for contaminants,volumetric properties, mechanistic properties, moisture content, QC/QAof construction materials in general.

In one embodiment, a penetrometer may be a device that is positionedseparate from a gauge housing. In one example, electrical signalsgenerated by components of the penetrometer may be communicated to anMPC in the gauge housing by wires and/or wireless communication.

According to one embodiment, a gauge penetrometer rod may be configuredwith electrical components for measuring electrical properties of asample material. Exemplary sample material properties that may bemeasured include impedance, permittivity, permeability, and conductivityas a function of frequency. FIG. 4 is a vertical cross-sectional view ofa material property gauge 400 including a rod with electrical componentsintegrated therein for use in measuring material sample propertiesaccording to an embodiment of the subject matter described herein.Referring to FIG. 4, gauge 400 is operable to accurately determine aproperty value of a construction material 402. Gauge 400 may measure aproperty value of soil in a transmission mode and measure a propertyvalue of asphalt in a backscatter mode.

A rod 404 may include electrical components integrated therein formeasuring electrical parameters associated with sample material 402. Inparticular, a conductive, exterior portion 406 of rod 404 may be coupledto electrical driving circuitry 408 operable to generate acousticalimpulses (energy) and random signal sweeps into sample material 402.Further, a conductive component 410 may be coupled to electrical drivingcircuitry 412, which may be operable to generate ultra-wideelectromagnetic microwave signals into sample material 402. Acousticenergy may be impulse excitations produced by an electric solenoid, avibration shaker, a magnetostrictive device, bender elements,piezoelectric-based devices, or any device suitable to produce impulseor frequency domain signals. The electric signals may be defined by oneor more oscillators. For a low band from about DC to about 30 Mhz, oneor more phase-locked voltage controlled oscillators (VCOs) may be usedfor differing frequencies. A maximum frequency depends on the materialunder test. Further, an insulator 414 may be positioned in rod 404 forisolating acoustical and electrical measurements from the total lengthof rod 404 and for reducing the loss of high frequency measurements ofcurrents in rod 404. As an alternative, time domain reflectometry (TDR)techniques may be used for generating acoustical impulses and electricalsignaling.

Gauge 400 may include an electromagnetic sensor 416 for detecting samplematerial responses to electrical inputs from rod 404. For example,electromagnetic sensor 416 may be a wideband spiral antenna operable todetect sample material responses to electrical pulse signals generatedby rod 404 and through time domain analysis. Further, for example, maybe configured for measuring dielectric properties of sample material402. Sensor 416 may be operable to generate an electrical signalrepresenting the sample material responses to the electrical inputs.

An acoustic detector 418 may be operable to detect sample materialresponses to acoustical inputs from rod 404. Exemplary acousticdetectors include a geophone and a triaxial accelerometer.Alternatively, for example, acoustic detector 418 may include an impulsesource for directing electromagnetic fields into sample material 402 andoperable to detect sample material responses to the input. Detector 418may be operable to generate an electrical signal representing the samplematerial responses to the acoustical inputs.

A PCB 420 may be operable to receive one or more of electrical signalsproduced by sensor 416 and detector 418 for use in determining propertyvalues associated with sample material 402. Further, PCB 420 may includea MPC 422 incorporating the data represented in the electrical signalsfor determining the property values. MPC 422 may include computerprogram instructions to determine the property values by using a portionor all of the data provided by sensor 416 and detector 418. For example,the data may be used for estimating a density of sample material 402and/or correcting a density estimation of sample material 402. MPC 422may be programmed with the equations and data described herein forestimating or determining the property value.

Further, MPC 422 may include suitable hardware, software, and/orfirmware components for implementing measurement and calibrationprocedures according to the subject matter described herein. MPC 422 mayinclude one or more processors and memory components. Exemplary MPCcomponents include one or more of pre-amplifiers, spectroscopic gradeGaussian amplifiers, peak detectors, and analog-to-digital converters(ADCs) for performing the processes described herein. Procedure status,feedback, density, and modulus measurement information may be presentedto an operator via one or more interfaces of gauge 100.

Gauge 400 may include an interface for receiving operator input and fordisplaying output to the operator. In particular, gauge 400 may includea display 422 for displaying output and a keypad 424 for receivingoperator input. A calculated property value of sample material 402 maybe displayed to an operator via display 422.

In one embodiment, gauge 400 may be positioned in a backscatter modesuch that end 426 is on a surface of a sample material. In this mode,the generation of acoustical energy on the sample material surface maylead to the preferential excitement of particular wave types, such asRayleigh waves, surface waves, shear waves, and/or compressional waves.Shear waves may also be generated by generating negative impulses. Byadding the two waveforms together, the compressional components can besubtracted out for calculation purposes.

The data of the electromagnetic and acoustical sample material responsesmay be combined in calculations for determining a property value ofsample material 402. The acoustical data is associated with yieldingmechanical properties. The electromagnetic data is associated withyielding chemical properties, such as moisture content, clay content,mica content, cement content, etc. Further, the electromagnetic data maybe correlated to mechanical properties, such as density. Calculationsperformed using acoustical data typically requires correction fordensity. Thus, electromagnetic and acoustical measurements may be usedin accordance with the subject matter described herein to determinesample material properties, such as density and/or modulus.

Gauges may include acoustic and electromagnetic field componentspositioned on a bottom surface of the gauge for operation in abackscatter mode. FIG. 5 illustrates a partial vertical cross-sectionalview of a portable seismic pavement analyzer (PSPA, DSPA) (or materialproperty gauge) 500 including acoustic and electromagnetic componentspositioned on a bottom surface of the gauge according to an embodimentof the subject matter described herein. Referring to FIG. 5, gauge 500may include a bottom surface 502 for positioning on a top surface 504 ofsample material 506. An electromagnetic sensor/detector 508 operable togenerate an electromagnetic field 510 and operable to detect a responseto electromagnetic field 510 by sample material 506.

Further, gauge 500 may include an acoustic energy generator 512 operableto generate acoustic energy. Acoustic detectors 514 and 516 may bepositioned in a spaced apart relationship with respect to one anotherand acoustic energy generator 512. Further, acoustic detectors 514 and516 may be operable to detect a response to the generated acousticenergy by sample material 506.

An MPC 518 may be in communication with components 508, 512, 514, and516 and operable to control the components and receive signalingrepresentative of the response to the acoustic energy andelectromagnetic field by sample material 506. The received signalingdata may be utilized as described herein for determining one or moreproperty values associated with sample material 506.

In one embodiment, void and temperature measurements may be made ofsample material for use in density estimations and correcting densityestimations. The total voids in a sample material is related to bulkdensity based on the maximum specific gravity (Gmm as described by ASTMstandard D-2041 and AASHTO standard T-209). Modulus and void ratio arerelated in HMA. FIG. 6 is a graph showing the linear relationshipbetween variations of a construction mix's void percentage and modulus.Further, the temperature of a sample material is related to bulk density(ASTM D-4311) and modulus. FIG. 7 is a graph showing the relationshipbetween variations of asphalt temperature and modulus. The subjectmatter described herein may correct for density estimations using knownrelationships between void measurements and/or temperature measurementsand modulus of a sample material. Further, correction for HMA modulusmay be obtained by temperature correction. Thus, a method fornon-nuclear density measurement may be implemented by the subject matterdescribed herein. In as much as the acoustical phase velocity is relatedto the variables of sheer modulus G and mass density ρ, andelectromagnetic methods are multi-variable and chaotic systems, thesystems described herein yield accurate and repeatable densitymeasurements.

According to one embodiment, the material property gauges describedherein may obtain moisture content measurements using a microwavemoisture meter. The microwave band used by a microwave moisture metermay be less susceptible to ionic effects or errors associated withmineralogy of an aggregate or soil than other moisture measuringdevices. FIG. 8 is a top perspective view of a microwave moisture meter800 for use in material property gauges according to the subject matterdescribed herein. Referring to FIG. 8, moisture meter 800 includes ametallic cavity filled with a high dielectric material 802. A 2.45 GHzdipole antenna 804 may be etched into a top surface of dielectricmaterial 802. In one example, a ceramic cover may be positioned overantenna 804 for protection. The self-impedance of antenna 804 may bemeasured at terminals 806. In particular, the impedance as a function offrequency may be measured at terminals 806. In one example, theresonance of the cavity-backed antenna may be measured as a function ofwater content. FIG. 9 is a graph showing frequency variations withrespect to moisture content.

In one embodiment, the permittivity of pavement construction materialmay be measured using lower frequency fringing or field couplingtechniques. FIG. 10A is a vertical cross-sectional view of an exemplarylower frequency fringing sensor 1000. Sensor 1000 may be used as anelectromagnetic sensor for detecting moisture in the gauges describedherein. In this example, sensor 1000 is a strip or linear sensor. Sensor1000 may also be used with gauges described herein to measure the voidcontent of an asphalt mix. Referring to FIG. 10A, sensor 1000 mayinclude conductors 1002, 1004, 1006, and 1007 and ground 1008. Conductor1006 is operable as a source. Conductor 1007 is operable as a pickup.Each conductor level may be separated by an epoxy board or FR4, which isa printed circuit board material having a dielectric constant of about4.2. Electric fields 1010 are emitted into soil 1012 and coupled back toconductor 1006. To a certain extent, as the frequency increases, theoutput voltage V₀ increases. This type of sensor may be particularlysuitable for measurements in the UHF radio range. In particular, as thedielectric constant of soil 1012 (or asphalt in the alternative)increases, the output voltage V₀ increases proportionally. Capacitancetechniques may be suitable for lower frequencies. Exemplary sensors aredescribed in U.S. Pat. Nos. 6,400,161; 6,677,763; 6,803,771; 5,900,736;and U.S. Patent Application Publication No. 2003/0222662, thedisclosures of which are incorporated herein by reference in theirentireties. By utilizing a suitable integrated circuit, the amplitudeand phase of a received signal may be digitized as a function offrequency, and the results analyzed for dispersion in theelectromagnetic domain.

FIG. 10B is a vertical cross-sectional view of another exemplary lowerfrequency fringing sensor 1014. Referring to FIG. 10B, sensor 1014 isrotational symmetric such that a “ring shape” is formed by each ofconductors 1016, 1018, and 1020. Conductor 1022 may form a disc-likeshape. Further, conductor 1022 is operable as the source. Conductor 1018is connected to ground 1024. During operation, fields may extend fromconductor 1022 through a construction material and to conductor 1020.The voltage at conductor 1020 may be substantially less than the voltageapplied at conductor 1022, but increases with the dielectric constant ofthe soil.

Sensors 1000 and 1014 shown in FIGS. 10A and 10B, respectively, may beformed in a variety of shapes. In particular, the sensors may becylindrical, circular, or linearly-shaped. Further, the sensors may besymmetric about a central axis. Further, suitable shielding may beapplied to the sensors for shielding stray or unintended fields.

Microwave-based moisture property detectors may be advantageous, forexample, because such detectors are known to yield density-independentmoisture measurements. Such detectors may be advantageous overneutron-based moisture property detectors, because neutron-baseddetectors are density and material dependent. Further, it is desirableto reduce the use of neutron sources because of NRC regulations and feesassociated with neutron sources.

The moisture property detector components may be positioned in anysuitable position in the interior or the exterior of a gauge. Forexample, a moisture signal source may be positioned in an end of asource rod for generating an electromagnetic field from within aninterior of a sample material. In this example, a moisture signaldetector may be positioned within a gauge housing for detecting theelectromagnetic field transmitted through the sample material andgenerating a signal representing the detected electromagnetic field.Further, the generated electromagnetic field may be an electromagneticpulse or step. In another example, a moisture signal source and detectormay be attached to a drill rod operable to penetrate a sample materialfor positioning the moisture signal source in the interior of the samplematerial. In this example, the moisture signal detector may generate asignal representative of detected electromagnetic fields, andcommunicate the signal via a wired or wireless communication connectionto an MPC in a gauge housing.

A moisture property detector according to the subject matter describedherein may include one or more of several electromagnetic-basedcomponents. For example, the moisture property detector may include aduroid patch antenna configured to detect an electromagnetic fieldgenerated by an electromagnetic field source. The resonance frequency orinput impedance may be monitored as a function of a dielectric constant.This moisture sensor operates in a self-impedance mode where the complexterminal impedance is measured at the input of the patch antenna feed.In this example, the patch may resonate at about 2.45 Ghz, where thereturn loss of the antenna is minimal and referred to as the resonancefrequency. As the water content increases, the dielectric constant ofthe medium increases, and thus increases the electric near field energy,and lowers the resonance frequency. Examples of this technique aredescribed in U.S. Pat. No. 5,072,172, the disclosure of which isincorporated herein by reference in its entirety.

In another example, a moisture property detector may include a monopole.The monopole is broadband and may detect DC to microwave electromagneticfields. In use, the monopole may be driven by an oscillator. Theimpedance may be measured as a function of frequency and various soilparameters obtained. Alternatively, the impulse response can be obtainedand convolution and transform theory by be applied for obtaining soilproperties. Further, the monopole may be coated by an insulator toreduce the energy loss in the soil.

During construction, the construction materials are typically exposed toan open air environment. Therefore, it is nearly impossible to controlmoisture content in most construction materials, especially roadconstruction materials. Thus, wet densities are measured with themoisture content, and the dry density is calculated based on the wetdensity measurements. ASTM standards D-2922 and D-3017, incorporatedherein by reference in their entireties, describe equations for drydensity back calculations. Further, water affects the modulus of samplematerial. Therefore, for modulus and density measurements, correction istypically needed due to moisture.

Density-independent moisture measurements may be made based on atwo-parameter measurement of attenuation (or magnitude) and phase shiftin a transmission- or reflection-type mode. Alternatively,density-independent moisture measurements may be made using microwavesat a single frequency. A two-parameter method may be implemented bycomparing the real and imaginary parts of the dielectric constant, asshown in the following equation (wherein ε represents the dielectricconstant):ε=ε(ω)′−jε(ω)″

A density independent calibration factor A(ψ) (wherein ψ is thewet-based volumetric water content) may be used for canceling densitycomponents. The principle of density-independent moisture measurementsis based on both the real and imaginary part of the dielectric constantbeing related to dry material and water constituents, which change as afunction of density. Density components may be empirically canceled bycombining ε(ρ_(d), ψ)′ and jε(ρ_(d), ψ)″ in the following equation:${A(\psi)} = \frac{{\varepsilon\left( {\rho_{d},\psi} \right)}^{\prime} - 1}{{\varepsilon\left( {\rho_{d},\psi} \right)}^{''}}$The above equation assumes that Ε(ω)′ and ε(ω)″ are linearly independentfunctions of ρ_(d) and ψ.

The loss tangent ε′/ε″ may describe the material interaction andresponse. The behavior of the complex permittivity implies thatnormalizing both ε(w)′ and jε(ω)″ with density may reduce densityeffects. Further, data pairs may be normalized with bulk density asfunctions of temperature and moisture content. The following equationprovides a measure of bulk density for particulate materials withoutprior knowledge of moisture content or temperature given that moisturedensity relationships are independent (wherein a_(f) represents slope, krepresents intercept, a_(f) is related to the frequency, and k relatedto the dry dielectric):ε″/ρ=a _(f)(ε′/ρ−k)Alternatively, the following equation provides a measure of bulkdensity:ρ=(a _(f)ε′−ε″)/ka _(f)

At high frequencies, water is the dominant factor associated with energyloss related to ε″ in the material, and the energy storage is related toε′. Both are inversely related to density. Thus, a density-independentfunction for water content is based on the loss tangent ε″/ε′.Therefore, again, by normalizing the loss tangent by the densityprovided by the above equation results in the following equation:ξ=ε″/(ε′(a _(f)ε′−ε″))Here, the constant ka_(f) is omitted, and the loss tangent has beennormalized, resulting in a moisture function with reduced densityeffects. Experimentally, for granular materials, it has been found that√ξ is linear with moisture content ka_(f) is a function of themeasurement frequency and remains constant for data pairs of ε′ and ε″when they have been normalized by density.

Based on experimental results, it can be shown that, as temperatureincreases, the bound water becomes easier to rotate and the dielectricconstant increases. Thus, for the water measurement, temperaturecorrection may be necessary.

Since ξ is a function of moisture content with the density effectsremoved, and since it is experimentally found to be linearly related tomoisture, calibration as a function of moisture and temperature can beimplemented by fitting to the following linear equation (wherein ξrepresents a linear value in moisture M, and b represents a constantthat is temperature dependent):√ξ=A*M+B(T)In this equation, the intercept B increases with temperature, but theslope A is constant. For granular materials, the following equation wasempirically derived (wherein temperature is measured in Celsius):B(T)=9.77×10⁻⁴ *T+0.206The moisture content may then be determined using the followingequation:% M=(√ξ(a _(f)ε′, ε″)−B(T))/AIn one embodiment, samples of soil may be extracted from the field andfit to this equation as a function of moisture yielding the constants Aand B at a particular temperature. Generic curves may also be definedwhereby a field offset is performed in use. Therefore, any moistureproperty detector operable to measure the real and/or imaginary portionsof the dielectric constant of a material at a single frequency, multiplefrequencies, or continuous sweeps of frequencies, chirps of frequencycontent, impulse responses and convolutions thereof, on the surface ordown-hole can be incorporated into embodiments of the subject matterdescribed herein.

Microwaves are more sensitive to free water than bound water but arealso a function of the constituents of the chemical makeup of the drymass and water mass mixture. However, a dry mass and water mass mixtureis less susceptible to ionic motion and DC conductivity when consideringthe following equation:ε=ε(ω)′−jε(ω)″=ε(ω)′−j(ε(ω)_(d)″+σ_(d.c.)/ωε₀

The higher frequencies reduce the effects of DC conductivity and measuremore of the dielectric permittivity. However, soil specific calibrationsmay still be necessary. The differences in the calibrations are muchsmaller than their low frequency counterparts. Thus, if the materialchanges slightly without a gauge operator's knowledge, suitable resultsmay still be obtained. Therefore, the microwave electromagnetictechniques have soil specific calibrations or offsets that may berequired when comparing sandy loams to clay classes of soils.

As stated above, microwave measurements may be used for moisturemeasurements. In one example, a cavity-backed, microwave, dipole antennamay be used to measure the resonant frequency of sand of differentmoisture contents. Further, suitable techniques may be used to obtainmaterial properties, such as moisture, porosity, clay content, andclassification, using wideband microwave dispersion measurements.

When an electromagnetic field is applied to a lossy sample material,current flows and charge is rearranged on the sample material. As aresult, a dipole-like electric field configuration on the samplematerial may be induced, and thus form a volume density of polarizationP and free charge current density J. These volume densities are a resultof constitutive parameters, dielectric constant ε(ω) and conductivityσ(ω). As soil material is non-homogeneous, the size of its particles,their relative geometry, orientation, and water content alter theresponse of electromagnetic waves in a complex manner. In general, forcertain materials (e.g., clay), the sample material shows significantdispersion, e.g., as frequency ω increases, dielectric constant εdecreases and conductivity σ increases. The effect is reduced for highfrequencies as compared to lower frequencies. Thus, sensors in themicrowave range may be used for moisture measurements. Further, sweepingthrough low frequencies may result in a measurement of dispersion foruse in classifying the sample material based on soil type.

In one example, soil content type and losses of sample material can beestimated by inspecting dielectric constant dispersion over a microwavebandwidth from DC to a few GHz. In particular, it has been shown thatthe type and amount of clay materials and the mineral-solution-interfacecharacteristics may be determined using frequency dependent propertiesof the electrical impedance of the sample material. These electricalproperties may be used in the measurement of soil porosity and strength,and used for classifying soil based on its sand/clay mixture. Further,these electrical properties may be used to calculate the modulus of asoil fabric. The acoustical and electromagnetic properties can be usedto infer soil values such as porosity, water content, saturation,specific gravity of the soil solids, and nature of the stiffness of thetortuous soil skeleton, which in turn lead to values of density, modulusand stiffness.

In summary, dielectric and acoustic properties including dispersion canaddress the following:

Soil classification cohesive vs. non-cohesive percents

Strength

Moisture content

Density

Porosity

Saturation

Specific gravity

Skeleton stiffness

Swelling

Corrosion

Organic/peat content

In non-clay (sand) materials, the dielectric constant ε and conductivityσ response is independent of frequency. On the other hand, in hydratedclay materials, a relaxation occurs wherein these quantities change withfrequency. FIG. 11A is a graph showing a comparison of dielectricconstants of clay material (cohesive soil) and non-clay material(non-cohesive soil) over different frequencies.

FIG. 11B is a graph showing the dielectric dispersion of theconductivity and dielectric constant of a cohesive soil. It is notedthat dielectric constant ε(ω) and conductivity σ(ω) are functions offrequency. The dielectric constant decreases and the conductivityincreases with increased frequency.

FIG. 11C is a graph showing dielectric constant dispersion of severaldifferent types of clays. Referring to FIG. 11C, it is apparent thatdifferent clays have different dispersion curves. Further, thedispersion depends on the mineralogy.

Information regarding dielectric constant dispersion for known materialsmay be used in the subject matter described herein for selectingcalibration curves for radiation detectors and moisture propertydetectors. Further, the subject matter described herein may be acombination asphalt and soils gauge having operability to measureasphalt layers in a backscatter mode and soils in a transmission mode.Further, for example, a fringing field planar detector may be attachedto a bottom surface of the gauge for simultaneously measuringelectromagnetic density. In this mode, the nuclear component cancalibrate the electromagnetic detectors in the field for improving thespeed of access to a capacitance asphalt density indicator. Furthermore,by investigating the dielectric constant of a top depth (e.g., 1 cmdepth) of material, an estimate of the surface roughness may be foundfor further nuclear density correction of rough surfaces. By comparingmultiple sensors with different penetration depths less than about 1 cm,relative correction factors may be obtained.

An inhomogeneous sample material has a frequency dependent permittivity.In particular, a two-layer sample material may be modeled with thefollowing equation (wherein ε_(r ∞) represents a high frequencydielectric constant, ε_(r s) is associated with the low frequencies, andτ represents the resonant time constant associated with a frequency1/τ):ε_(r)(ω)=ε_(r ∞+)(ε_(r s−)ε_(r ∞))/(1+ω²τ²)−jωτ(ε_(r s−)ε_(r ∞))/(1+ω²τ²)This model may be used with soil classification techniques describedherein for determining sample material properties, such as moisturecontent and density. Other dielectric dispersion techniques may be usedfor addressing soil classification cohesive/non-cohesive percentages,strength, moisture content, density, porosity, swelling, corrosion, andorganic/peat content. Additional discussion is provided in U.S. patentapplication Ser. No. 10/971,546, filed Oct. 22, 2004 (U.S. PatentApplication Publication No. 2005/015028), commonly assigned, and thedisclosure of which is incorporated herein by reference in its entirety.

FIG. 12 illustrates a schematic diagram of an exemplary materialproperty gauge 1200 including acoustical impedance and electricalimpedance functionality according to an embodiment of the subject matterdescribed herein. Referring to FIG. 12, gauge 1200 may include anelectromagnetic field sensor 1202, an electromagnetic generator 1204,acoustic detectors 1206 and 1208, an acoustic generator 1210, and apenetrometer 1212. Gauge 1200 is operable to measure responses byconstruction material 1214 to an electromagnetic field and acousticalenergy. Further, gauge 1200 may use the response data for determiningone or more property values of construction material 1214, such asmechanistic values, volumetric values, and moisture content.

Penetrometer 1212 is a metal conductive rod having an insulative sheathon its exterior and a 60° cone tip 1216 for insertion into constructionmaterial 1214. Penetrometer 1212 may include components for use inmeasuring complex electrical parameters such as permittivity,permeability, and conductivity as a function of frequency.Electromagnetic generator 1204 and acoustic generator 1210 may beoperably connected to penetrometer 1212 for emitting an electromagneticfield and acoustic energy waves from the interior of constructionmaterial 1214. The response of construction material 1214 to the emittedacoustic energy may be measured by acoustic detectors 1206 and 1208. Theresponse of construction material 1214 to the emitted electromagneticfield may be measured by electromagnetic sensor 1202. In an alternativeembodiment, penetrometer 1212 may be configured in a self-impedance modeas described herein for measuring impedance at driving point terminals.

In one example, penetrometer 1212 may function as a monopole. In thisexample, ground shielding may be provided by a conducting aluminum base1218. Electromagnetic source 1204 may be swept from low frequency toresonance frequency, and the impedance of construction material 1214obtained. Back calculation may provide complex permittivity as afunction of frequency, which is tabulated as the dielectric constant,conductivity, and the dispersive parameters, or the total decrease fromlow frequency to high frequency may be the changes in the dielectricconstant or conductivity.

Calibrations may be stored in a memory of gauge 1200 for use in thefield. When using a calibration routine, an offset may be required formoisture, density, or modulus measurements in field use. For asphalt,typical mixes include limestone and granite of several gradations andasphalt contents. For soils, several mixtures of clay and sand may bemodeled into field selectable calibration routines, as described in moredetail herein. The operator may have some prior knowledge of theconstruction material to be tested, and select a proper model based onthe prior knowledge. Alternatively, the actual asphalt mix or soil fromthe base or sub-base of construction material may be physicallycharacterized in a laboratory for moisture content, density, andmodulus, and the data stored in a calibration routine for field use.Further, in the alternative, an adaptive and learning patternrecognition signal processes may be used for calibrating the gauge, suchas a specialized algorithm, soft decision classification, basisshrinkage kernels, fuzzy logic, and neural networks. These processes maybe used in a gauge according to the subject matter described herein foridentifying and classifying soil type, for calculating moisture content,density, and modulus.

The insulative sheath on penetrometer 1212 may provide isolation betweenthe acoustical measurements and the total length of penetrometer 1212.Further, the insulative sheath can function as an electrical insulatorso that high frequency measurements have a reduced loss as the currentstravel down the “monopole” of penetrometer 1212.

Acoustic detector 1206 may be a wideband spiral antenna that receives anelectrical pulse signal from penetrometer 1212. By using time domaintechniques, calculations may be performed using an MPC 1220 fordetermining average electrical parameters and for correlating theparameters to density and moisture content. Acoustic detector 1208 maybe, for example, a geophone, triaxial accelerometer, or the like. In thealternative, acoustic detector 1208 may be replaced by an acousticenergy source for generating an acoustic impulse on the surface ofmaterial 1214 for detection and analysis.

The admittance of a probing antenna at low frequencies is known to berelated to the electrical properties of the earth by the followingequation (wherein C_(air) represents the capacitance of the antenna in adielectric medium of 1, and Y represents the admittance, i.e., theinverse of impedance):Y=jωC _(air)(ε_(r)−σ/ωε_(o))For higher frequencies, the antenna may resonate and, generally, theimpedance is provided by the following equation (wherein V representsthe volume of integration, Z_(o) represents the impedance of free space,E represents the vector field in the lossy medium, and E′ is the vectorelectric field vector in free space):Z _(v) =Z _(o)−(jω/l ²)∫(ε−ε_(o))E·E′dVIn use, a rational function of several coefficients may be used todescribe the permittivity sensor, where calibration in at least 2different mediums is required to determine the coefficients. Backcalculation of the admittance or impedance may yield the permittivityand conductance of the pavement material.

In one embodiment, a pulse or step of acoustic energy maybe applied topenetrometer 1212 for emission into construction material. The responseof the construction material to the pulse or step may be measured byacoustic detector 1208 for analysis of travel time. The phase velocityand loss through the medium may be used, as described herein, tocalculate the conductivity and dielectric constant of the material.Exemplary techniques for calibrations of different soils versus densityare described by ASTM standard D-6780, the contents of which aredisclosed by reference herein in its entirety.

In one embodiment, the gauge described herein may be configured with aradiation source and radiation detector for receiving a response toradiation by a sample material. The radiation response data may be usedin combination with acoustic energy response data and/or electromagneticfield response data for determining a property of the sample material.For example, a density of a sample material may be estimated usingradiation response data. In this example, acoustic energy response dataand/or electromagnetic field response data may be used for correctingthe density estimation based on the radiation response data.

As set forth above, a material property gauge according to the subjectmatter described herein may be utilized by an operator in a field and/orlaboratory environment for obtaining property values of a samplematerial, such as a construction material. In particular, a materialproperty gauge may be used for obtaining mechanistic, volumetric, andmoisture content values associated with a construction material.Property value measurements may be determined using gauge 100 shown inFIGS. 1A and 2A configured in either a transmission mode or abackscatter mode. FIG. 13 is a flow chart illustrating an exemplaryprocess for property measurements using gauge 100 configured in atransmission mode or a backscatter mode according to an embodiment ofthe subject matter described herein. Referring to FIG. 13, in block1300, gauge 100 is positioned on a top surface of construction material106 as shown in FIG. 1A in a transmission mode, wherein penetrometer 104is lowered into an interior of construction material 106. Alternatively,gauge 100 is positioned on a top surface of construction material 106 asshown in FIG. 2A in a backscatter mode, wherein penetrometer 104 israised such that tip end 102 is on a surface of construction material106.

In block 1302, the operator may use display 152 and keypad 154 to selectwhether gauge 100 is configured in a transmission or backscatter mode.Based on the operator selection, the components of PCB 130 may be setfor calculations in the selected mode.

In block 1304, based on the selected operational mode and the selectedone of the transmission mode or the backscatter mode, the components ofPCB 130 may activate acoustic sources and/or electromagnetic sources forproducing acoustic energy and/or an electromagnetic field, respectively.

In block 1306, the components of PCB 130 may control the acousticdetectors and/or electromagnetic field sensors to measure/detectresponses by construction material 106. Further, in one embodiment,temperature sensor 142 may be activated for sensing a temperatureassociated with construction material 106 for use in property valuecalculations. The measured/detected responses associated withconstruction material 106 may include P-wave seismic velocity (V_(P)),S-wave seismic velocity (V_(S)), K-bulk wave seismic velocity (V_(B)),dispersive real part of permittivity (ε′(ω)), dispersive imaginary partof permittivity (ε″(ω)), dispersive real part of conductivity (σ′(ω)),dispersive imaginary part of permittivity (σ′(ω)), Maxwell-Wagnerrelaxation time constant (τ), temperature for corrections, instrumenteddynamic cone penetrometer outputs (e.g., force, energy, acceleration,and moisture), total dielectric dispersion from low to high frequenciesabove Maxwell-Wagner effects (Δε), and total conductance dispersion fromlow to high frequencies above Maxwell-Wagner effects (Δσ). Theseexemplary values may be referred to as constitutive parameters inelectromagnetics and acoustics.

In block 1308, signals may be produced by acoustic detectors,electromagnetic field sensors, and/or the temperature sensorrepresenting the measured and/or detected responses by constructionmaterial 106. The signals may be communicated to MPC 151 for use incalculating the property values.

In block 1310, MPC 151 may calculate one or more property valuesassociated with construction material 106 based upon the producedsignals. MPC 151 may apply the data in the signals to one or more of theequations described herein for estimating property values and/orcorrecting property value estimations. An operator may select whether astored process in MPC 151 is to determine classification of material,and therefore select calibration coefficients. In particular, theoperator may select to either of the following: (1) MPC 151 providecalibration coefficients; (2) the operator selects material type andcalibration curves; and (3) a generic calibration that shows increasesor decreases in relative values. After the type of calibration isselected, pattern recognition signal processing algorithms may be usedto calculate property values, such as moisture, density, and modulus.

In block 1312, the calculated property values may be displayed to theoperator. For example, the property values may be displayed via display152.

As stated above, a material property gauge in accordance with thesubject matter described herein may be used for surface analysis of aconstruction material. FIG. 14 is a flow chart illustrating an exemplaryprocess for property measurements using gauge 100 for surface analysisaccording to an embodiment of the subject matter described herein.Referring to FIG. 14, in block 1400, the operator may determine whetherto use gauge 100 for property value measurements of asphalt or soil. Ifasphalt is determined, the operator may position gauge in thebackscatter mode (block 1402). Otherwise, if soil is determined, theprocess proceeds to block 1404.

In block 1406, gauge 100 may produce an electromagnetic field. Further,in block 1408, gauge 100 may produce acoustical energy. The response ofthe construction material to the electromagnetic field may be measuredby electromagnetic sensor 132 of gauge 100 (block 1410). Further, theresponse of the construction material to the acoustical energy may bedetected by acoustic detectors 124 and 126 (block 1412).

In block 1414, gauge 100 may determine whether to conduct moistureanalysis for use in correcting property value determinations, such asdensity or modulus. In one example, the operator may select to conductmoisture analysis. In another example, MPC 151 may determine whether toconduct moisture analysis. If it is determined not to conduct moistureanalysis, one or more property values may be determined for the asphaltwithout the use of moisture value corrections (block 1416).

If it is determined to conduct moisture analysis, moisture values may becalculated (block 1418) and applied for correcting for moisture (block1420). The moisture value calculations may be used in block 1416 forcalculating one or more property values for asphalt (block 1416).

For measuring soil, in block 1404, the operator may select to configuregauge 100 in a transmission mode or a backscatter mode and manuallyconfigure gauge 100 for operation in the selected mode. If backscattermode is selected, gauge 100 may produce an electromagnetic field andacoustical energy into the soil (block 1422). The response of theconstruction material to the electromagnetic field and the acousticalenergy may be detected by gauge 100 (block 1424). Next, calculations forproperty values of the soil may be calculated based on the response(block 1426).

If the transmission mode is selected in block 1404, a depth forpenetrometer 104 may be selected and a hole of suitable depth defined inthe soil. The penetrometer may be placed in the hole in the transmissionmode configuration. Gauge 100 may produce an electromagnetic field andacoustical energy into the soil (block 1430). The response of theconstruction material to the electromagnetic field and the acousticalenergy may be detected by gauge 100 (block 1432). Next, calculations forproperty values of the soil may be calculated based on the response(block 1434). Instrumented pentrometers can obtain information about thesoil strata for example soil strength (density, modulus) as a functionof depth, which can be included in the data storage for signalprocessing. This information can aid the final analysis of the state ofthe soil.

FIG. 15 is a flow chart illustrating an exemplary process for measuringsoil modulus according to an embodiment of the subject matter describedherein. Gauge 100 shown in FIGS. 1A and 2A is referenced in thisexemplary process. Referring to FIG. 15, in block 1500, the operator mayselect to configure gauge 100 in a transmission mode or a backscattermode. If a transmission mode is selected, the operator may configuregauge 100 in the transmission mode as shown in FIG. 1A. (block 1502). Ifa backscatter mode is selected, the operator may configure gauge 100 inthe backscatter mod as shown in FIG. 2A (block 1504).

In block 1506, gauge 100 may produce an electromagnetic field andacoustical energy into the soil. The response of the soil to theelectromagnetic field and the acoustical energy may be detected by gauge100 (block 1508). For example, layered stratified data may be obtainedfrom an IDCP.

In block 1510, an error correction matrix may be built using the rawdata of the response. The raw data may be corrected using MPC 151 forproducing error corrected data in accordance with the processes andtechniques described herein (block 1512). Soil property values ofinterest may be mapped using adaptive signal processing (block 1514). Inblock 1516, a moisture value, such as moisture content, may bedetermined. Systematic error correction can also be applied here. Thisincludes the gauge calibration to take manage inaccuracies of theelectronic and mechanical components of the gauge.

Next, in block 1518, it is determined whether to calculate modulus ordensity for the soil. The determination may be made, for example, basedon operator selection of modulus or density. If modulus is determined, amoisture correction process as described herein may be applied fordetermining corrected property values (block 1520). Further, theproperty values may be displayed and stored (block 1522).

If density is determined in block 1518, an acoustic-to-density mappingroutine may be applied (block 1522) and the moisture correction processapplied as described herein for determining corrected property values(block 1520). The property values may be displayed and stored (block1522).

Density may be calculated acoustically or electromagnetically. Thesevalues can be used alone or averaged together as they are obtainedindependently. Modulus can be calculated independently, as theelectromagnetic values can yield void ratios which can be implemented inpredictive equations.

FIG. 16 is a flow chart illustrating an exemplary process for measuringasphalt modulus according to an embodiment of the subject matterdescribed herein. Gauge 100 shown in FIGS. 1A and 2A is referenced inthis exemplary process. Referring to FIG. 16, in block 1600, theoperator may configure gauge 100 in a backscatter mode as shown in FIG.2A. In block 1602, gauge 100 may produce an electromagnetic field andacoustical energy into the asphalt. The response of the asphalt to theelectromagnetic field and the acoustical energy may be detected by gauge100 (block 1604). Further, in block 1606, raw moisture data iscalculated from the response.

Next, in block 1608, it is determined whether to calculate modulus ordensity for the asphalt. The determination may be made, for example,based on operator selection of modulus or density. Appropriatecalibration curves may be obtained (block 1610). Next, the calibrationcurves, response data, and moisture data may be used for calculatingmodulus or density. The modulus or density values may be displayed andstored (block 1612).

FIG. 17 is a block diagram illustrating operation of a material propertygauge 1700 according to an embodiment of the subject matter describedherein. Referring to FIG. 17, gauge 1700 includes a display, computersystem, digital storage, signal processing equipment, calibrationmodels, and material models, as represented by block 1702. Duringoperation, gauge 1700 may switch between either one of anelectromagnetic mode 1704 and an acoustic mode 1706 electromagnetic oracoustic measurements, respectively, as described herein. Inelectromagnetic generation mode 1704, gauge 1700 may apply anelectromagnetic field to a construction material 1708. When inelectromagnetic generation mode 1704, gauge 1700 may also function in anelectromagnetic receive mode 1710 for receiving response by material1708. In acoustic generation mode 1706, gauge 1700 may apply acousticenergy to construction material 1708. When in acoustic generation mode1706, gauge 1700 may also function in an acoustic receive mode 1712 forreceiving response by material 1708. The responses can includeelectromagnetic and acoustic constitutive parameters of material 1708.The response data can be used for calculating property values ofmaterial 1708 according to the subject matter described herein.

FIG. 18 is a block diagram illustrating operation of a material propertygauge 1800 according to an embodiment of the subject matter describedherein. Referring to FIG. 18, gauge 1800 includes includes a display,computer system, digital storage, signal processing equipment,calibration models, and material models, as represented by block 1802.During operation, gauge 1800 may switch between either one of aself-impedance (or reflection-type) mode and a transmission typemeasurement mode, as described herein. Gauge 1800 may include atransmitter 1804 and one or more receivers 1806. The transmission maytransmit electromagnetic or acoustic energy into a construction material1808. Receivers 1806 may receive a response by material 1808 to thetransmitted electromagnetic or acoustic energy. Further, gauge may beconfigured for transmission in a backscatter mode and/or transmissionmode as described herein. The responses may be used by gauge 1800 forcalculating property values of material 1808 according to the subjectmatter described herein.

FIG. 19 is a flow chart illustrating an exemplary process forcalculating a property value of a construction material according to anembodiment of the subject matter described herein. Referring to FIG. 19,an MPC in a material property gauge according to the subject matterdescribed herein may receive one or more predetermined calibrationmodels (block 1900), initial estimates (block 1902), and materialproperty measured responses by a construction material toelectromagnetic fields and/or acoustic energy (block 1904). The initialestimates may include one or more of the following root finders andpredetermined calibration curves.

In block 1906, the predetermined calibration models and measuredresponses may be applied to a material model. An expected response basedon the inputs and material model may be determined at block 1908. Theexpected response may include an expected curve, which is a function ofthe multiple parameters and the construction material's response toinput electromagnetic fields and/or acoustic energy.

In block 1910, the expected response determined in block 1908 iscompared to the measured response of block 1904. Based on thecomparison, an error may be generated at block 1912. Next, in block1914, it is determined whether the error is less than a predeterminederror value. If the error is not less than the predetermined errorvalue, coefficients are adjusted (block 1916) and the process returns toblock 1906. Otherwise, property values for the construction material arecalculated and displayed (block 1918).

Material property gauges according to the subject matter describedherein may be operable in several different modes of operation forobtaining measurements for use in calculating property values of sampleor construction materials. For example, the gauge may be configured formeasuring acoustic energies in either a down hole or upholeconfiguration. In the down hole configuration, a penetrometer of thegauge may be positioned in a transmission mode. In an upholeconfiguration, a penetrometer of the gauge may be positioned in abackscatter mode. Further, a gauge may be positioned in a down hole modefor obtaining dielectric measurements of water, dispersion measurementsfor soil density, and classification-related information. Further, agauge may be positioned in a backscatter mode for using anelectromagnetic generator/source for obtaining electromagnetic fieldmeasurements for asphalt density calculations. Further, a gauge may bepositioned in a backscatter mode for using an acoustic source forobtaining acoustic energy measurements for modulus and soil densitycalculations. Further, in one embodiment, a combination of acousticmeasurements, dispersive measurements, and electromagnetic dispersionmeasurements may be used for calculations of density, modulus, andcorrection data based on moisture and temperature measurements.

It will be understood that various details of the subject matterdescribed herein may be changed without departing from the scope of thesubject matter described herein. Furthermore, the foregoing descriptionis for the purpose of illustration only, and not for the purpose oflimitation, as the subject matter described herein is defined by theclaims as set forth hereinafter.

1. A material property gauge for determining a property of constructionmaterial, the material property gauge comprising: (a) an electromagneticsensor operable to measure a response of construction material to anelectromagnetic field and operable to produce a signal representing themeasured response by the construction material to the electromagneticfield; (b) an acoustic detector operable to detect a response of theconstruction material to acoustical energy and operable to produce asignal representing the detected response by the construction materialto the acoustical energy; and (c) a material property calculationfunction configured to calculate a property value associated with theconstruction material based upon the signals produced by theelectromagnetic sensor and the acoustic detector.
 2. The materialproperty gauge of claim 1 wherein the electromagnetic sensor comprises adevice selected from the group consisting of a fringing field sensor,capacitance sensor, a microwave nearfield sensor, a microwave resonator,waveguide sensor, transmission line sensor, an antenna, combinations ofabove and the like.
 3. The material property gauge of claim 1 whereinthe construction material comprises a material selected from the groupconsisting of soil, asphalt, pavement, stone, sub-base material, andsub-grade material.
 4. The material property gauge of claim 1 whereinthe acoustic detector comprises a device selected from the groupconsisting of a geophone, an accelerometer, a vibration sensor,piezoelectric component, an inductive coil, a magnetostrictivecomponent, a bender element, micro-electro-mechanical system(MEMS)-based device a seismic pavement analyzer, and a stiffness gauge,a falling weight deflectometer, dynamic cone penetrometer, and aHumboldt stiffness gauge.
 5. The material property gauge of claim 1comprising an electromagnetic field generator operable to emit theelectromagnetic field into the construction material.
 6. The materialproperty gauge of claim 5 wherein the electromagnetic field generatorcomprises a device selected from the group consisting of a voltagecontrolled oscillator (VCO), a Clapp oscillator, a relaxationoscillator, a ring oscillator, an RC oscillator, a crystal oscillator, ablocking oscillator, a phase-locked oscillator, a voltage oscillator, amultivibrator, a Gunn diode, a numerically-controlled oscillator, aKystron tube, a high-power microwave magnetron, a backward waveoscillator, a VLF transmitter, an integrated circuit timer, an arbitrarywaveform generator, a pulse-wide modulation device, an analogsynthesizer, current sources, synthesized sources, YIG-tunedoscillators, and integrated circuits.
 7. The material property gauge ofclaim 1 wherein the material property calculation function is configuredto calculate a density of the construction material based on the signalsproduced by the electromagnetic sensor and the acoustic detector.
 8. Thematerial property gauge of claim 1 wherein the material propertycalculation function is configured to correct a density calculation ofthe construction material based on the signal produced by theelectromagnetic sensor.
 9. The material property gauge of claim 8wherein the signal produced by the electromagnetic sensor represents amoisture property value associated with the construction material. 10.The material property gauge of claim 1 wherein the material propertycalculation function is configured to correct a density calculation ofthe construction material based on the signal produced by the acousticsensor.
 11. The material property gauge of claim 1 wherein the materialproperty calculation function is configured to calculate one or more ofa density, a moisture value, and a modulus of the construction materialbased on the signals produced by the electromagnetic sensor and theacoustic detector.
 12. The material property gauge of claim 11 whereinthe signal produced by the electromagnetic sensor represents a voidsvalue associated with the construction material.
 13. The materialproperty gauge of claim 1 comprising an acoustic generator operable toemit the acoustical energy into the construction material.
 14. Thematerial property gauge of claim 13 wherein the acoustic generatorcomprises a device selected from the group consisting of a penetrometer,a Clegg Hammer, a falling weight deflectometer, a Briaud compactiondevice, and an FWD, a geophone, an accelerometer, a vibration sensor, apiezoelectric device, an inductive coil-based device, a magnetostrictivedevice, a bender element, and micro-electro-mechanical system(MEMS)-based device electromechanical shakers, solenoid activatedhammers, instrumented hammers, frequency domain devices, and time domaindevices.
 15. The material property gauge of claim 1 comprising a displayoperable to display the property value associated with theelectromagnetic sensor and the acoustic detector.
 16. The materialproperty gauge of claim 1 comprising a penetrometer operable to measureat least one of moisture, density, and modulus of the constructionmaterial, and wherein the material property calculation function isconfigured to correct a density or modulus calculations of theconstruction material based on the measured at least one of moisture,density, and modulus.
 17. A material property gauge for determining aproperty of construction material, the material property gaugecomprising: (a) an electromagnetic sensor operable to measure a responseof construction material to an electromagnetic field and operable toproduce a signal representing the measured response by the constructionmaterial to the electromagnetic field; (b) a temperature sensor operableto measure a temperature associated with the construction material andoperable to produce a signal representing the measured temperatureassociated with the construction material; and (c) a material propertycalculation function configured to calculate a property value associatedwith the construction material based upon the signals produced by theelectromagnetic sensor and the temperature sensor.
 18. The materialproperty gauge of claim 17 wherein the electromagnetic sensor comprisesa device selected from the group consisting of a fringing field sensor,a microwave nearfield sensor, a microwave resonator, and an antenna. 19.The material property gauge of claim 17 wherein the constructionmaterial comprises a material selected from the group consisting ofsoil, asphalt, pavement, stone, sub-base material, and sub-gradematerial.
 20. The material property gauge of claim 17 wherein thetemperature sensor comprises a device selected from the group consistingof an infrared heat sensor, an optical infrared sensor, a resistancetemperature detector (RTD), a thermocouple, a solid state-basedtemperature sensor, and a resistive-based temperature sensor.
 21. Thematerial property gauge of claim 17 comprising an electromagnetic fieldgenerator operable to emit the electromagnetic field into theconstruction material.
 22. The material property gauge of claim 21wherein the electromagnetic field generator comprises a device selectedfrom the group consisting of a voltage controlled oscillator (VCO), aClapp oscillator, a relaxation oscillator, a ring oscillator, an RCoscillator, a crystal oscillator, a blocking oscillator, a phase-lockedoscillator, a voltage oscillator, a multivibrator, a Gunn diode, anumerically-controlled oscillator, a Kystron tube, a high-powermicrowave magnetron, a backward wave oscillator, a VLF transmitter, anintegrated circuit timer, an arbitrary waveform generator, a pulse-widemodulation device, an analog synthesizer, current sources, synthesizedsources, YIG-tuned oscillators, and integrated circuits.
 23. Thematerial property gauge of claim 17 wherein the material propertycalculation function is configured to calculate a density of theconstruction material based on the signals produced by theelectromagnetic sensor and the temperature sensor.
 24. The materialproperty gauge of claim 17 wherein the material property calculationfunction is configured to correct a density calculation of theconstruction material based on the signal produced by theelectromagnetic sensor.
 25. The material property gauge of claim 24wherein the signal produced by the electromagnetic sensor represents amoisture property value associated with the construction material. 26.The material property gauge of claim 17 wherein the material propertycalculation function is configured to correct a density calculation ofthe construction material based on the signal produced by thetemperature sensor.
 27. The material property gauge of claim 17 whereinthe signal produced by the electromagnetic sensor represents a voidsvalue associated with the construction material.
 28. The materialproperty gauge of claim 17 wherein the material property calculationfunction is configured to calculate one or more of a density, a moisturevalue, and a modulus of the construction material based on the signalsproduced by the electromagnetic sensor and the temperature sensor. 29.The material property gauge of claim 17 comprising a display operable todisplay the property value associated with the electromagnetic sensorand the temperature sensor.
 30. A method for determining a property ofconstruction material, the method comprising: (a) measuring a responseof construction material to an electromagnetic field; (b) producing asignal representing the measured response by the construction materialto the electromagnetic field; (c) detecting a response of theconstruction material to acoustical energy; (d) producing a signalrepresenting the detected response by the construction material to theacoustical energy; and (e) calculating a property value associated withthe construction material based upon the produced signals.
 31. Themethod of claim 30 wherein the construction material comprises amaterial selected from the group consisting of soil, asphalt, pavement,stone, sub-base material, sub-grade material, and concrete.
 32. Themethod of claim 30 wherein calculating a property value associated withthe construction material includes calculating one of a density, amoisture value, and a modulus of the construction material based on theproduced signals.
 33. The method of claim 30 comprising correcting adensity calculation of the construction material based on the signalproduced by the electromagnetic sensor.
 34. The method of claim 30comprising correcting a density calculation of the construction materialbased on the signal representing the measured response by theconstruction material to the electromagnetic field.
 35. The method ofclaim 30 comprising emitting the acoustical energy into the constructionmaterial.
 36. The method of claim 30 comprising displaying thecalculated property value.
 37. A method for determining a property ofconstruction material, the method comprising: (a) measuring a responseof construction material to an electromagnetic field; (b) producing asignal representing the measured response by the construction materialto the electromagnetic field; (c) detecting a response of theconstruction material to temperature; (d) producing a signalrepresenting the detected response by the construction material to thetemperature; and (e) calculating a property value associated with theconstruction material based upon the produced signals.
 38. The method ofclaim 37 wherein the construction material comprises a material selectedfrom the group consisting of soil, asphalt, pavement, stone, sub-basematerial, and sub-grade material.
 39. The method of claim 37 whereincalculating a property value associated with the construction materialincludes calculating one of a density, a moisture value, and modulus ofthe construction material based on the produced signals.
 40. The methodof claim 37 comprising correcting a density calculation of theconstruction material based on the signal produced by theelectromagnetic sensor.
 41. The method of claim 37 comprising correct adensity calculation of the construction material based on the signalrepresenting the measured response by the construction material to theelectromagnetic field.
 42. The method of claim 37 comprising displayingthe calculated property value.
 43. A computer program product comprisingcomputer executable instruction embodied in a computer readable mediumfor performing steps comprising: (a) measuring a response ofconstruction material to an electromagnetic field; (b) producing asignal representing the measured response by the construction materialto the electromagnetic field; (c) detecting a response of theconstruction material to acoustical energy; (d) producing a signalrepresenting the detected response by the construction material to theacoustical energy; and (e) calculating a property value associated withthe construction material based upon the produced signals.
 44. Thecomputer program product of claim 43 wherein the construction materialcomprises a material selected from the group consisting of soil,asphalt, pavement, stone, sub-base material, and sub-grade material. 45.The computer program product of claim 43 wherein calculating a propertyvalue associated with the construction material includes calculating oneof a density, a moisture value, and a modulus of the constructionmaterial based on the produced signals.
 46. The computer program productof claim 43 comprising correcting a density calculation of theconstruction material based on the signal produced by theelectromagnetic sensor.
 47. The computer program product of claim 43comprising correct a density calculation of the construction materialbased on the signal representing the measured response by theconstruction material to the electromagnetic field.
 48. The computerprogram product of claim 43 comprising emitting the acoustical energyinto the construction material.
 49. The computer program product ofclaim 43 comprising displaying the calculated property value.
 50. Acomputer program product comprising computer executable instructionembodied in a computer readable medium for performing steps comprising:(a) measuring a response of construction material to an electromagneticfield; (b) producing a signal representing the measured response by theconstruction material to the electromagnetic field; (c) detecting aresponse of the construction material to temperature; (d) producing asignal representing the detected response by the construction materialto the temperature; and (e) calculating a property value associated withthe construction material based upon the produced signals.
 51. Thecomputer program product of claim 50 wherein the construction materialcomprises a material selected from the group consisting of soil,asphalt, pavement, stone, sub-base material, sub-grade material, cement.52. The computer program product of claim 50 wherein calculating aproperty value associated with the construction material includescalculating one of a density, a moisture value, and a modulus of theconstruction material based on the produced signals.
 53. The computerprogram product of claim 50 comprising correcting a density calculationof the construction material based on the signal produced by theelectromagnetic sensor.
 54. The computer program product of claim 50comprising correct a density calculation of the construction materialbased on the signal representing the measured response by theconstruction material to the electromagnetic field.
 55. The computerprogram product of claim 50 comprising displaying the calculatedproperty value.